diff --git a/doc/INDEXEDDB.md b/doc/INDEXEDDB.md
new file mode 100644
index 0000000000..ebfa65800e
--- /dev/null
+++ b/doc/INDEXEDDB.md
@@ -0,0 +1,73 @@
+## Promises, async/await and indexedDB
+
+Doesn't indexedDB close your transaction if you don't queue more requests from an idb event handler?
+So wouldn't that mean that you can't use promises and async/await when using idb?
+
+It used to be like this, and for IE11 on Win7 (not on Windows 10 strangely enough), it still is like this.
+Here we manually flush the promise queue synchronously at the end of an idb event handler.
+
+In modern browsers, indexedDB transactions should only be closed after flushing the microtask queue of the event loop,
+which is where promises run.
+
+Keep in mind that indexedDB events, just like any other DOM event, are fired as macro tasks.
+Promises queue micro tasks, of which the queue is drained before proceeding to the next macro task.
+This also means that if a transaction is completed, you will only receive the event once you are ready to process the next macro tasks.
+That doesn't prevent any placed request from throwing TransactionInactiveError though.
+
+## TransactionInactiveError in Safari
+
+Safari doesn't fully follow the rules above, in that if you open a transaction,
+you need to "use" (not sure if this means getting a store or actually placing a request) it straight away,
+without waiting for any *micro*tasks. See comments about Safari at https://github.com/dfahlander/Dexie.js/issues/317#issue-178349994.
+
+Another failure mode perceived in Hydrogen on Safari is that when the (readonly) prepareTxn in sync wasn't awaited to be completed before opening and using the syncTxn.
+I haven't found any documentation online about this at all. Awaiting prepareTxn.complete() fixed the issue below. It's strange though the put does not fail.
+
+What is happening below is:
+ - in the sync loop:
+    - we first open a readonly txn on inboundGroupSessions, which we don't use in the example below
+    - we then open a readwrite txn on session, ... (does not overlap with first txn)
+        - first the first incremental sync on a room (!YxKeAxtNcDZDrGgaMF:matrix.org) it seems to work well
+        - on a second incremental sync for that same room, the first get throws TransactionInactiveError for some reason.
+        - the put in the second incremental sync somehow did not throw.
+
+So it looks like safari doesn't like (some) transactions still being active while a second one is being openened, even with non-overlapping stores.
+For now I haven't awaited every read txn in the app, as this was the only place it fails, but if this pops up again in safari, we might have to do that.
+
+Keep in mind that the `txn ... inactive` logs are only logged when the "complete" or "abort" events are processed,
+which happens in a macro task, as opposed to all of our promises, which run in a micro task.
+So the transaction is likely to have closed before it appears in the logs.
+
+```
+[Log] txn 4504181722375185 active on inboundGroupSessions
+[Log] txn 861052256474256 active on session, roomSummary, roomState, roomMembers, timelineEvents, timelineFragments, pendingEvents, userIdentities, groupSessionDecryptions, deviceIdentities, outboundGroupSessions, operations, accountData
+[Info] hydrogen_session_5286139994689036.session.put({"key":"sync","value":{"token":"s1572540047_757284957_7660701_602588550_435736037_1567300_101589125_347651623_132704","filterId":"2"}})
+[Info] hydrogen_session_5286139994689036.userIdentities.get("@bwindels:matrix.org")
+[Log] txn 4504181722375185 inactive
+[Log]  * applying sync response to room !YxKeAxtNcDZDrGgaMF:matrix.org ...
+[Info] hydrogen_session_5286139994689036.roomMembers.put({"roomId":"!YxKeAxtNcDZDrGgaMF:matrix.org","userId":"@bwindels:matrix.org","membership":"join","avatarUrl":"mxc://matrix.org/aerWVfICBMcyFcEyREcivLuI","displayName":"Bruno","key":"!YxKeAxtNcDZDrGgaMF:matrix.org|@bwindels:matrix.org"})
+[Info] hydrogen_session_5286139994689036.roomMembers.get("!YxKeAxtNcDZDrGgaMF:matrix.org|@bwindels:matrix.org")
+[Info] hydrogen_session_5286139994689036.timelineEvents.add({"fragmentId":0,"eventIndex":2147483658,"roomId":"!YxKeAxtNcDZDrGgaMF:matrix.org","event":{"content":{"body":"haha","msgtype":"m.text"},"origin_server_ts":1601457573756,"sender":"@bwindels:matrix.org","type":"m.room.message","unsigned":{"age":8360},"event_id":"$eD9z73-lCpXBVby5_fKqzRZzMVHiPzKbE_RSZzqRKx0"},"displayName":"Bruno","avatarUrl":"mxc://matrix.org/aerWVfICBMcyFcEyREcivLuI","key":"!YxKeAxtNcDZDrGgaMF:matrix.org|00000000|8000000a","eventIdKey":"!YxKeAxtNcDZDrGgaMF:matrix.org|$eD9z73-lCpXBVby5_fKqzRZzMVHiPzKbE_RSZzqRKx0"})
+[Info] hydrogen_session_5286139994689036.roomSummary.put({"roomId":"!YxKeAxtNcDZDrGgaMF:matrix.org","name":"!!!test8!!!!!!","lastMessageBody":"haha","lastMessageTimestamp":1601457573756,"isUnread":true,"encryption":null,"lastDecryptedEventKey":null,"isDirectMessage":false,"membership":"join","inviteCount":0,"joinCount":2,"heroes":null,"hasFetchedMembers":false,"isTrackingMembers":false,"avatarUrl":null,"notificationCount":5,"highlightCount":0,"tags":{"m.lowpriority":{}}})
+[Log] txn 861052256474256 inactive
+[Info] syncTxn committed!!
+
+... two more unrelated sync responses ...
+
+[Log] starting sync request with since s1572540191_757284957_7660742_602588567_435736063_1567300_101589126_347651632_132704 ...
+[Log] txn 8104296957004707 active on inboundGroupSessions
+[Log] txn 2233038992157489 active on session, roomSummary, roomState, roomMembers, timelineEvents, timelineFragments, pendingEvents, userIdentities, groupSessionDecryptions, deviceIdentities, outboundGroupSessions, operations, accountData
+[Info] hydrogen_session_5286139994689036.session.put({"key":"sync","value":{"token":"s1572540223_757284957_7660782_602588579_435736078_1567300_101589130_347651633_132704","filterId":"2"}})
+[Log]  * applying sync response to room !YxKeAxtNcDZDrGgaMF:matrix.org ...
+[Info] hydrogen_session_5286139994689036.roomMembers.get("!YxKeAxtNcDZDrGgaMF:matrix.org|@bwindels:matrix.org")
+[Warning] stopping sync because of error
+[Error] StorageError: get("!YxKeAxtNcDZDrGgaMF:matrix.org|@bwindels:matrix.org") failed on txn with stores accountData, deviceIdentities, groupSessionDecryptions, operations, outboundGroupSessions, pendingEvents, roomMembers, roomState, roomSummary, session, timelineEvents, timelineFragments, userIdentities on hydrogen_session_5286139994689036.roomMembers: (name: TransactionInactiveError) (code: 0) Failed to execute 'get' on 'IDBObjectStore': The transaction is inactive or finished.
+    (anonymous function)
+    asyncFunctionResume
+    (anonymous function)
+    promiseReactionJobWithoutPromise
+    promiseReactionJob
+[Log] newStatus – "SyncError"
+[Log] txn 8104296957004707 inactive
+[Log] txn 2233038992157489 inactive
+```
diff --git a/prototypes/idb-promises-es6.html b/prototypes/idb-promises-es6.html
new file mode 100644
index 0000000000..ef7d357d15
--- /dev/null
+++ b/prototypes/idb-promises-es6.html
@@ -0,0 +1,112 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+</head>
+<body>
+    <script type="text/javascript" src="promifill.js"></script>
+    <!-- <script src="https://cdn.jsdelivr.net/npm/promise-polyfill@8/dist/polyfill.min.js"></script> -->
+    <script type="text/javascript">
+        //window.Promise = Promifill;
+        function reqAsPromise(req) {
+            return new Promise(function (resolve, reject) {
+                req.onsuccess = function() {
+                    resolve(req);
+                    Promise.flushQueue && Promise.flushQueue();
+                };
+                req.onerror = function(e) {
+                    reject(new Error("IDB request failed: " + e.target.error.message));
+                    Promise.flushQueue && Promise.flushQueue();
+                };
+            });
+        }
+
+        function Storage(databaseName) {
+            this._databaseName = databaseName;
+            this._database = null;
+        }
+
+        Storage.prototype = {
+            open: function() {
+                const req = window.indexedDB.open(this._databaseName);
+                const self = this;
+                req.onupgradeneeded = function(ev) {
+                    const db = ev.target.result;
+                    const oldVersion = ev.oldVersion;
+                    self._createStores(db, oldVersion);
+                }; 
+                return reqAsPromise(req).then(function() {
+                    self._database = req.result;
+                });
+            },
+            openTxn: function(mode, storeName) {
+                const txn = this._database.transaction([storeName], mode);
+                const store = txn.objectStore(storeName);
+                return Promise.resolve(store);
+            },
+            _createStores: function(db) {
+                db.createObjectStore("foos", {keyPath: ["id"]});
+            }
+        };
+
+        function getAll(store) {
+            const request = store.openCursor();
+            const results = [];
+            return new Promise(function(resolve, reject) {
+                request.onsuccess = function(event) {
+                    const cursor = event.target.result;
+                    if(cursor) {
+                        results.push(cursor.value);
+                        cursor.continue();
+                    } else {
+                        resolve(results);
+                        Promise.flushQueue && Promise.flushQueue();
+                    }
+                };
+                request.onerror = function(e) {
+                    reject(new Error("IDB request failed: " + e.target.error.message));
+                    Promise.flushQueue && Promise.flushQueue();
+                };
+            });
+        }
+
+        async function main() {
+            try {
+                let storage = new Storage("idb-promises");
+                await storage.open();
+                const store = await storage.openTxn("readwrite", "foos");
+                store.clear();
+                store.add({id: 5, name: "foo"});
+                store.add({id: 6, name: "bar"});
+                console.log("all1", await getAll(store));
+                store.add({id: 7, name: "bazzz"});
+                console.log("all2", await getAll(store));
+            } catch(err) {
+                console.error(err.message + ": " + err.stack);
+            };
+        }
+        main();
+
+
+        /*
+        
+        we basically want something like this for IE11/Win7:
+            
+            return new Promise(function (resolve, reject) {
+                req.onsuccess = function() {
+                    resolve(req);
+                    Promise?.flushQueue();
+                };
+                req.onerror = function(e) {
+                    reject(new Error("IDB request failed: " + e.target.error.message));
+                    Promise?.flushQueue();
+                };
+            });
+
+        we don't have this problem on platforms with a native promise implementation, so we can just have our own (forked) promise polyfill? 
+         */
+    </script>
+</body>
+</html>
+ 
diff --git a/prototypes/idb-promises-safari.html b/prototypes/idb-promises-safari.html
new file mode 100644
index 0000000000..00f8174f7d
--- /dev/null
+++ b/prototypes/idb-promises-safari.html
@@ -0,0 +1,169 @@
+<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+</head>
+<body>
+    <script type="text/javascript">
+        function reqAsPromise(req) {
+            return new Promise(function (resolve, reject) {
+                req.onsuccess = function() {
+                    resolve(req.result);
+                };
+                req.onerror = function(e) {
+                    reject(new Error("IDB request failed: " + req.error));
+                };
+            });
+        }
+        function txnAsPromise(txn) {
+            return new Promise(function (resolve, reject) {
+                txn.oncomplete = function() {
+                    resolve(txn);
+                };
+                txn.onabort = function(e) {
+                    reject(new Error("Transaction got aborted: " + txn.error));
+                };
+            });
+        }
+
+        const BrowserMutationObserver = window.MutationObserver || window.WebKitMutationObserver;
+
+        function useMutationObserver(flush) {
+          let iterations = 0;
+          const observer = new BrowserMutationObserver(flush);
+          const node = document.createTextNode('');
+          observer.observe(node, { characterData: true });
+
+          return () => {
+            node.data = (iterations = ++iterations % 2);
+          };
+        }
+
+        const wait = (function() {
+            let resolve = null;
+            const trigger = useMutationObserver(() => {
+                resolve();
+            });
+            return () => {
+                return new Promise(r => {
+                    resolve = r;
+                    trigger();
+                });
+            };
+        })();
+        
+        
+        var _resolve = Promise.resolve.bind(Promise);
+        var _then = Promise.prototype.then;
+
+        async function delay() {
+            return Promise.resolve();
+            // two consecutive macro tasks
+            //await new Promise(r => setImmediate(r));
+            // the next macro task will now be the complete event of the txn,
+            // so schedule another macro task to execute after that
+            //await new Promise(r => setImmediate(r));
+            //return;
+            // for (let i = 0; i < 1000; i+=1) {
+            //         console.log("await...");
+            //         await wait();
+            //     }
+            let p = _resolve(0);
+            for (let i=0;i<10;++i) {
+                p = _then.call(p, x => x + 1);
+            }
+            let result = await p;
+            console.log("Result: "+ result + " (should be 10)");
+        }
+
+        class Storage {
+            constructor(databaseName) {
+                this._databaseName = databaseName;
+                this._database = null;
+            }
+
+            open() {
+                const req = window.indexedDB.open(this._databaseName);
+                const self = this;
+                req.onupgradeneeded = function(ev) {
+                    const db = ev.target.result;
+                    const oldVersion = ev.oldVersion;
+                    self._createStores(db, oldVersion);
+                }; 
+                return reqAsPromise(req).then(function() {
+                    self._database = req.result;
+                });
+            }
+
+            openTxn(mode, storeName) {
+                const txn = this._database.transaction([storeName], mode);
+                txn.addEventListener("complete", () => {
+                    console.info(`transaction ${mode} for ${storeName} completed`);
+                });
+                txn.addEventListener("abort", e => {
+                    console.warn(`transaction ${mode} for ${storeName} aborted`, e.target.error);
+                });
+                return txn;
+            }
+
+            _createStores(db) {
+                db.createObjectStore("foos", {keyPath: "id"});
+            }
+        }
+
+        async function getAll(store, depth = 0) {
+            if (depth < 15) {
+                return await getAll(store, depth + 1);
+            } 
+            const request = store.openCursor();
+            const results = [];
+            return await new Promise(function(resolve, reject) {
+                request.onsuccess = function(event) {
+                    const cursor = event.target.result;
+                    if(cursor) {
+                        results.push(cursor.value);
+                        cursor.continue();
+                    } else {
+                        resolve(results);
+                        Promise.flushQueue && Promise.flushQueue();
+                    }
+                };
+                request.onerror = function(e) {
+                    reject(new Error("IDB request failed: " + e.target.error.message));
+                    Promise.flushQueue && Promise.flushQueue();
+                };
+            });
+        }
+
+        async function main() {
+            try {
+                let storage = new Storage("idb-promises");
+                await storage.open();
+                //await reqAsPromise(storage.openTxn("readwrite", "foos").objectStore("foos").clear());
+
+                for (let i = 0; i < 10; i += 1) {
+                    storage.openTxn("readonly", "foos").objectStore("foos").get(5);
+                    //console.log("from readtxn", await reqAsPromise(storage.openTxn("readonly", "foos").objectStore("foos").get(5)));
+                    const txn = storage.openTxn("readwrite", "foos");
+                    const store = txn.objectStore("foos");
+                    console.log("writing the foos");
+                    store.put({id: 5, name: "foo"});
+                    store.put({id: 6, name: "bar"});
+                    store.put({id: 7, name: "bazzz"});
+                    await delay();
+                    console.log("reading the foos");
+                    console.log("5", await reqAsPromise(store.get(5)));
+                    console.log("6", await reqAsPromise(store.get(6)));
+                    console.log("7", await reqAsPromise(store.get(7)));
+                    // await txnAsPromise(txn);
+                }
+            } catch(err) {
+                console.error(err);
+            };
+        }
+        main();
+    </script>
+</body>
+</html>
+ 
diff --git a/src/legacy-polyfill.js b/src/legacy-polyfill.js
index 0ce493e0c5..c3c8263b96 100644
--- a/src/legacy-polyfill.js
+++ b/src/legacy-polyfill.js
@@ -15,6 +15,14 @@ limitations under the License.
 */
 
 // polyfills needed for IE11
+import Promise from "../lib/es6-promise/index.js";
+import {checkNeedsSyncPromise} from "./matrix/storage/idb/utils.js";
+
+if (typeof window.Promise === "undefined") {
+    window.Promise = Promise;
+    // TODO: should be awaited before opening any session in the picker
+    checkNeedsSyncPromise();
+}
 import "core-js/stable";
 import "regenerator-runtime/runtime";
 import "mdn-polyfills/Element.prototype.closest";
@@ -24,14 +32,6 @@ import "mdn-polyfills/Element.prototype.closest";
 // it will also include the file supporting *all* the encodings,
 // weighing a good extra 500kb :-(
 import "text-encoding";
-import {checkNeedsSyncPromise} from "./matrix/storage/idb/utils.js";
-import Promise from "../lib/es6-promise/index.js";
-
-if (typeof window.Promise === "undefined") {
-    window.Promise = Promise;
-    // TODO: should be awaited before opening any session in the picker
-    checkNeedsSyncPromise();
-}
 
 // TODO: contribute this to mdn-polyfills
 if (!Element.prototype.remove) {
diff --git a/src/matrix/DeviceMessageHandler.js b/src/matrix/DeviceMessageHandler.js
index 854c901b08..e09041333a 100644
--- a/src/matrix/DeviceMessageHandler.js
+++ b/src/matrix/DeviceMessageHandler.js
@@ -80,7 +80,7 @@ export class DeviceMessageHandler {
         if (!this._olmDecryption) {
             return;
         }
-        const readTxn = await this._storage.readTxn([this._storage.storeNames.session]);
+        const readTxn = this._storage.readTxn([this._storage.storeNames.session]);
         const pendingEvents = await this._getPendingEvents(readTxn);
         if (pendingEvents.length === 0) {
            return;
@@ -91,7 +91,7 @@ export class DeviceMessageHandler {
         for (const err of decryptChanges.errors) {
             console.warn("decryption failed for event", err, err.event);
         }
-        const txn = await this._storage.readWriteTxn([
+        const txn = this._storage.readWriteTxn([
             // both to remove the pending events and to modify the olm account
             this._storage.storeNames.session,
             this._storage.storeNames.olmSessions,
diff --git a/src/matrix/Session.js b/src/matrix/Session.js
index ef535fc7b3..3c2f0e8c3b 100644
--- a/src/matrix/Session.js
+++ b/src/matrix/Session.js
@@ -164,13 +164,13 @@ export class Session {
         }
         const key = await ssssKeyFromCredential(type, credential, this._storage, this._cryptoDriver, this._olm);
         // and create session backup, which needs to read from accountData
-        const readTxn = await this._storage.readTxn([
+        const readTxn = this._storage.readTxn([
             this._storage.storeNames.accountData,
         ]);
         await this._createSessionBackup(key, readTxn);
         // only after having read a secret, write the key
         // as we only find out if it was good if the MAC verification succeeds
-        const writeTxn = await this._storage.readWriteTxn([
+        const writeTxn = this._storage.readWriteTxn([
             this._storage.storeNames.session,
         ]);
         try {
@@ -217,7 +217,7 @@ export class Session {
             await this._e2eeAccount.uploadKeys(this._storage);
             await this._deviceMessageHandler.decryptPending(this.rooms);
 
-            const txn = await this._storage.readTxn([
+            const txn = this._storage.readTxn([
                 this._storage.storeNames.session,
                 this._storage.storeNames.accountData,
             ]);
@@ -231,7 +231,7 @@ export class Session {
     }
 
     async load() {
-        const txn = await this._storage.readTxn([
+        const txn = this._storage.readTxn([
             this._storage.storeNames.session,
             this._storage.storeNames.roomSummary,
             this._storage.storeNames.roomMembers,
@@ -276,7 +276,7 @@ export class Session {
     async start(lastVersionResponse) {
         if (lastVersionResponse) {
             // store /versions response
-            const txn = await this._storage.readWriteTxn([
+            const txn = this._storage.readWriteTxn([
                 this._storage.storeNames.session
             ]);
             txn.session.set("serverVersions", lastVersionResponse);
@@ -284,7 +284,7 @@ export class Session {
             await txn.complete();
         }
 
-        const opsTxn = await this._storage.readWriteTxn([
+        const opsTxn = this._storage.readWriteTxn([
             this._storage.storeNames.operations
         ]);
         const operations = await opsTxn.operations.getAll();
@@ -341,17 +341,18 @@ export class Session {
             deviceMessageDecryptionPending: false
         };
         const syncToken = syncResponse.next_batch;
-        const deviceOneTimeKeysCount = syncResponse.device_one_time_keys_count;
-
-        if (this._e2eeAccount && deviceOneTimeKeysCount) {
-            changes.e2eeAccountChanges = this._e2eeAccount.writeSync(deviceOneTimeKeysCount, txn);
-        }
         if (syncToken !== this.syncToken) {
             const syncInfo = {token: syncToken, filterId: syncFilterId};
             // don't modify `this` because transaction might still fail
             txn.session.set("sync", syncInfo);
             changes.syncInfo = syncInfo;
         }
+
+        const deviceOneTimeKeysCount = syncResponse.device_one_time_keys_count;
+        if (this._e2eeAccount && deviceOneTimeKeysCount) {
+            changes.e2eeAccountChanges = this._e2eeAccount.writeSync(deviceOneTimeKeysCount, txn);
+        }
+        
         if (this._deviceTracker) {
             const deviceLists = syncResponse.device_lists;
             if (deviceLists) {
diff --git a/src/matrix/Sync.js b/src/matrix/Sync.js
index 14655b8e80..3bdf7d9d70 100644
--- a/src/matrix/Sync.js
+++ b/src/matrix/Sync.js
@@ -184,19 +184,23 @@ export class Sync {
         const roomStates = this._parseRoomsResponse(response.rooms, isInitialSync);
         await this._prepareRooms(roomStates);
         let sessionChanges;
-        const syncTxn = await this._openSyncTxn();
+        const syncTxn = this._openSyncTxn();
         try {
+            sessionChanges = await this._session.writeSync(response, syncFilterId, syncTxn);
             await Promise.all(roomStates.map(async rs => {
                 console.log(` * applying sync response to room ${rs.room.id} ...`);
                 rs.changes = await rs.room.writeSync(
                     rs.roomResponse, isInitialSync, rs.preparation, syncTxn);
             }));
-            sessionChanges = await this._session.writeSync(response, syncFilterId, syncTxn);
         } catch(err) {
             // avoid corrupting state by only
             // storing the sync up till the point
             // the exception occurred
-            syncTxn.abort();
+            try {
+                syncTxn.abort();
+            } catch (abortErr) {
+                console.error("Could not abort sync transaction, the sync response was probably only partially written and may have put storage in a inconsistent state.", abortErr);
+            } 
             throw err;
         }
         try {
@@ -221,24 +225,26 @@ export class Sync {
         };
     }
 
-    async _openPrepareSyncTxn() {
+    _openPrepareSyncTxn() {
         const storeNames = this._storage.storeNames;
-        return await this._storage.readTxn([
+        return this._storage.readTxn([
             storeNames.inboundGroupSessions,
         ]);
     }
 
     async _prepareRooms(roomStates) {
-        const prepareTxn = await this._openPrepareSyncTxn();
+        const prepareTxn = this._openPrepareSyncTxn();
         await Promise.all(roomStates.map(async rs => {
             rs.preparation = await rs.room.prepareSync(rs.roomResponse, rs.membership, prepareTxn);
         }));
+        // This is needed for safari to not throw TransactionInactiveErrors on the syncTxn. See docs/INDEXEDDB.md
+        await prepareTxn.complete();
         await Promise.all(roomStates.map(rs => rs.room.afterPrepareSync(rs.preparation)));
     }
 
-    async _openSyncTxn() {
+    _openSyncTxn() {
         const storeNames = this._storage.storeNames;
-        return await this._storage.readWriteTxn([
+        return this._storage.readWriteTxn([
             storeNames.session,
             storeNames.roomSummary,
             storeNames.roomState,
@@ -250,7 +256,7 @@ export class Sync {
             storeNames.groupSessionDecryptions,
             storeNames.deviceIdentities,
             // to discard outbound session when somebody leaves a room
-            // and to create room key messages when somebody leaves
+            // and to create room key messages when somebody joins
             storeNames.outboundGroupSessions,
             storeNames.operations,
             storeNames.accountData,
diff --git a/src/matrix/e2ee/Account.js b/src/matrix/e2ee/Account.js
index c0cfd8de1c..7b4a5b0dd1 100644
--- a/src/matrix/e2ee/Account.js
+++ b/src/matrix/e2ee/Account.js
@@ -45,7 +45,7 @@ export class Account {
         }
         const pickledAccount = account.pickle(pickleKey);
         const areDeviceKeysUploaded = false;
-        const txn = await storage.readWriteTxn([
+        const txn = storage.readWriteTxn([
             storage.storeNames.session
         ]);
         try {
@@ -212,7 +212,7 @@ export class Account {
     }
 
     async _updateSessionStorage(storage, callback) {
-        const txn = await storage.readWriteTxn([
+        const txn = storage.readWriteTxn([
             storage.storeNames.session
         ]);
         try {
diff --git a/src/matrix/e2ee/DeviceTracker.js b/src/matrix/e2ee/DeviceTracker.js
index cc3a421517..bf6f1403b6 100644
--- a/src/matrix/e2ee/DeviceTracker.js
+++ b/src/matrix/e2ee/DeviceTracker.js
@@ -68,7 +68,7 @@ export class DeviceTracker {
         }
         const memberList = await room.loadMemberList();
         try {
-            const txn = await this._storage.readWriteTxn([
+            const txn = this._storage.readWriteTxn([
                 this._storage.storeNames.roomSummary,
                 this._storage.storeNames.userIdentities,
             ]);
@@ -149,7 +149,7 @@ export class DeviceTracker {
         }).response();
 
         const verifiedKeysPerUser = this._filterVerifiedDeviceKeys(deviceKeyResponse["device_keys"]);
-        const txn = await this._storage.readWriteTxn([
+        const txn = this._storage.readWriteTxn([
             this._storage.storeNames.userIdentities,
             this._storage.storeNames.deviceIdentities,
         ]);
@@ -252,7 +252,7 @@ export class DeviceTracker {
      * @return {[type]}        [description]
      */
     async devicesForTrackedRoom(roomId, hsApi) {
-        const txn = await this._storage.readTxn([
+        const txn = this._storage.readTxn([
             this._storage.storeNames.roomMembers,
             this._storage.storeNames.userIdentities,
         ]);
@@ -268,7 +268,7 @@ export class DeviceTracker {
     }
 
     async devicesForRoomMembers(roomId, userIds, hsApi) {
-        const txn = await this._storage.readTxn([
+        const txn = this._storage.readTxn([
             this._storage.storeNames.userIdentities,
         ]);
         return await this._devicesForUserIds(roomId, userIds, txn, hsApi);
@@ -298,7 +298,7 @@ export class DeviceTracker {
             queriedDevices = await this._queryKeys(outdatedIdentities.map(i => i.userId), hsApi);
         }
 
-        const deviceTxn = await this._storage.readTxn([
+        const deviceTxn = this._storage.readTxn([
             this._storage.storeNames.deviceIdentities,
         ]);
         const devicesPerUser = await Promise.all(upToDateIdentities.map(identity => {
diff --git a/src/matrix/e2ee/RoomEncryption.js b/src/matrix/e2ee/RoomEncryption.js
index 94af64d1bf..90b6fd23f7 100644
--- a/src/matrix/e2ee/RoomEncryption.js
+++ b/src/matrix/e2ee/RoomEncryption.js
@@ -183,7 +183,7 @@ export class RoomEncryption {
                     console.warn("Got session key back from backup with different sender key, ignoring", {session, senderKey});
                     return;
                 }
-                const txn = await this._storage.readWriteTxn([this._storage.storeNames.inboundGroupSessions]);
+                const txn = this._storage.readWriteTxn([this._storage.storeNames.inboundGroupSessions]);
                 let roomKey;
                 try {
                     roomKey = await this._megolmDecryption.addRoomKeyFromBackup(
@@ -251,6 +251,7 @@ export class RoomEncryption {
         await this._deviceTracker.trackRoom(this._room);
         const megolmResult = await this._megolmEncryption.encrypt(this._room.id, type, content, this._encryptionParams);
         if (megolmResult.roomKeyMessage) {
+            // TODO: should we await this??
             this._shareNewRoomKey(megolmResult.roomKeyMessage, hsApi);
         }
         return {
@@ -273,7 +274,7 @@ export class RoomEncryption {
         const userIds = Array.from(devices.reduce((set, device) => set.add(device.userId), new Set()));
 
         // store operation for room key share, in case we don't finish here
-        const writeOpTxn = await this._storage.readWriteTxn([this._storage.storeNames.operations]);
+        const writeOpTxn = this._storage.readWriteTxn([this._storage.storeNames.operations]);
         let operationId;
         try {
             operationId = this._writeRoomKeyShareOperation(roomKeyMessage, userIds, writeOpTxn);
@@ -290,7 +291,7 @@ export class RoomEncryption {
         await this._sendRoomKey(roomKeyMessage, devices, hsApi);
 
         // remove the operation
-        const removeOpTxn = await this._storage.readWriteTxn([this._storage.storeNames.operations]);
+        const removeOpTxn = this._storage.readWriteTxn([this._storage.storeNames.operations]);
         try {
             removeOpTxn.operations.remove(operationId);
         } catch (err) {
@@ -329,7 +330,7 @@ export class RoomEncryption {
         this._isFlushingRoomKeyShares = true;
         try {
             if (!operations) {
-                const txn = await this._storage.readTxn([this._storage.storeNames.operations]);
+                const txn = this._storage.readTxn([this._storage.storeNames.operations]);
                 operations = await txn.operations.getAllByTypeAndScope("share_room_key", this._room.id);
             }
             for (const operation of operations) {
@@ -339,7 +340,7 @@ export class RoomEncryption {
                 }
                 const devices = await this._deviceTracker.devicesForRoomMembers(this._room.id, operation.userIds, hsApi);
                 await this._sendRoomKey(operation.roomKeyMessage, devices, hsApi);
-                const removeTxn = await this._storage.readWriteTxn([this._storage.storeNames.operations]);
+                const removeTxn = this._storage.readWriteTxn([this._storage.storeNames.operations]);
                 try {
                     removeTxn.operations.remove(operation.id);
                 } catch (err) {
diff --git a/src/matrix/e2ee/megolm/Encryption.js b/src/matrix/e2ee/megolm/Encryption.js
index cb0dddf8fc..a0769ba18c 100644
--- a/src/matrix/e2ee/megolm/Encryption.js
+++ b/src/matrix/e2ee/megolm/Encryption.js
@@ -54,7 +54,7 @@ export class Encryption {
     async encrypt(roomId, type, content, encryptionParams) {
         let session = new this._olm.OutboundGroupSession();
         try {
-            const txn = await this._storage.readWriteTxn([
+            const txn = this._storage.readWriteTxn([
                 this._storage.storeNames.inboundGroupSessions,
                 this._storage.storeNames.outboundGroupSessions,
             ]);
diff --git a/src/matrix/e2ee/olm/Decryption.js b/src/matrix/e2ee/olm/Decryption.js
index a193e0163a..7c4ef7e6b0 100644
--- a/src/matrix/e2ee/olm/Decryption.js
+++ b/src/matrix/e2ee/olm/Decryption.js
@@ -67,7 +67,7 @@ export class Decryption {
             return this._senderKeyLock.takeLock(senderKey);
         }));
         try {
-            const readSessionsTxn = await this._storage.readTxn([this._storage.storeNames.olmSessions]);
+            const readSessionsTxn = this._storage.readTxn([this._storage.storeNames.olmSessions]);
             // decrypt events for different sender keys in parallel
             const senderKeyOperations = await Promise.all(Array.from(eventsPerSenderKey.entries()).map(([senderKey, events]) => {
                 return this._decryptAllForSenderKey(senderKey, events, timestamp, readSessionsTxn);
diff --git a/src/matrix/e2ee/olm/Encryption.js b/src/matrix/e2ee/olm/Encryption.js
index 919acc4507..ff5f1a8ffa 100644
--- a/src/matrix/e2ee/olm/Encryption.js
+++ b/src/matrix/e2ee/olm/Encryption.js
@@ -98,7 +98,7 @@ export class Encryption {
     }
 
     async _findExistingSessions(devices) {
-        const txn = await this._storage.readTxn([this._storage.storeNames.olmSessions]);
+        const txn = this._storage.readTxn([this._storage.storeNames.olmSessions]);
         const sessionIdsForDevice = await Promise.all(devices.map(async device => {
             return await txn.olmSessions.getSessionIds(device.curve25519Key);
         }));
@@ -213,7 +213,7 @@ export class Encryption {
     }
 
     async _loadSessions(encryptionTargets) {
-        const txn = await this._storage.readTxn([this._storage.storeNames.olmSessions]);
+        const txn = this._storage.readTxn([this._storage.storeNames.olmSessions]);
         // given we run loading in parallel, there might still be some
         // storage requests that will finish later once one has failed.
         // those should not allocate a session anymore.
@@ -239,7 +239,7 @@ export class Encryption {
     }
 
     async _storeSessions(encryptionTargets, timestamp) {
-        const txn = await this._storage.readWriteTxn([this._storage.storeNames.olmSessions]);
+        const txn = this._storage.readWriteTxn([this._storage.storeNames.olmSessions]);
         try {
             for (const target of encryptionTargets) {
                 const sessionEntry = createSessionEntry(
diff --git a/src/matrix/room/Room.js b/src/matrix/room/Room.js
index 369836ee53..f12da45b25 100644
--- a/src/matrix/room/Room.js
+++ b/src/matrix/room/Room.js
@@ -82,7 +82,7 @@ export class Room extends EventEmitter {
         let retryEntries;
         if (retryEventIds) {
             retryEntries = [];
-            txn = await this._storage.readTxn(stores);
+            txn = this._storage.readTxn(stores);
             for (const eventId of retryEventIds) {
                 const storageEntry = await txn.timelineEvents.getByEventId(this._roomId, eventId);
                 if (storageEntry) {
@@ -99,7 +99,7 @@ export class Room extends EventEmitter {
             // check we have not already decrypted the most recent event in the room
             // otherwise we know that the messages for this room key will not update the room summary
             if (!sinceEventKey || !sinceEventKey.equals(this._syncWriter.lastMessageKey)) {
-                txn = await this._storage.readTxn(stores.concat(this._storage.storeNames.timelineFragments));
+                txn = this._storage.readTxn(stores.concat(this._storage.storeNames.timelineFragments));
                 const candidateEntries = await this._readRetryDecryptCandidateEntries(sinceEventKey, txn);
                 retryEntries = this._roomEncryption.findAndCacheEntriesForRoomKey(roomKey, candidateEntries);
             }
@@ -138,7 +138,7 @@ export class Room extends EventEmitter {
     _decryptEntries(source, entries, inboundSessionTxn = null) {
         const request = new DecryptionRequest(async r => {
             if (!inboundSessionTxn) {
-                inboundSessionTxn = await this._storage.readTxn([this._storage.storeNames.inboundGroupSessions]);
+                inboundSessionTxn = this._storage.readTxn([this._storage.storeNames.inboundGroupSessions]);
             }
             if (r.cancelled) return;
             const events = entries.filter(entry => {
@@ -155,7 +155,7 @@ export class Room extends EventEmitter {
                 // read to fetch devices if timeline is open
                 stores.push(this._storage.storeNames.deviceIdentities);
             }
-            const writeTxn = await this._storage.readWriteTxn(stores);
+            const writeTxn = this._storage.readWriteTxn(stores);
             let decryption;
             try {
                 decryption = await changes.write(writeTxn);
@@ -387,7 +387,7 @@ export class Room extends EventEmitter {
             }
         }).response();
 
-        const txn = await this._storage.readWriteTxn([
+        const txn = this._storage.readWriteTxn([
             this._storage.storeNames.pendingEvents,
             this._storage.storeNames.timelineEvents,
             this._storage.storeNames.timelineFragments,
@@ -490,7 +490,7 @@ export class Room extends EventEmitter {
     async _getLastEventId() {
         const lastKey = this._syncWriter.lastMessageKey;
         if (lastKey) {
-            const txn = await this._storage.readTxn([
+            const txn = this._storage.readTxn([
                 this._storage.storeNames.timelineEvents,
             ]);
             const eventEntry = await txn.timelineEvents.get(this._roomId, lastKey);
@@ -511,7 +511,7 @@ export class Room extends EventEmitter {
 
     async clearUnread() {
         if (this.isUnread || this.notificationCount) {
-            const txn = await this._storage.readWriteTxn([
+            const txn = this._storage.readWriteTxn([
                 this._storage.storeNames.roomSummary,
             ]);
             let data;
diff --git a/src/matrix/room/RoomSummary.js b/src/matrix/room/RoomSummary.js
index 81a68b8feb..39b1d1b333 100644
--- a/src/matrix/room/RoomSummary.js
+++ b/src/matrix/room/RoomSummary.js
@@ -272,7 +272,7 @@ export class RoomSummary {
         if (data === this._data) {
             return false;
         }
-        const txn = await storage.readWriteTxn([
+        const txn = storage.readWriteTxn([
             storage.storeNames.roomSummary,
         ]);
         try {
diff --git a/src/matrix/room/members/load.js b/src/matrix/room/members/load.js
index a8648eac75..aa14d2fbd2 100644
--- a/src/matrix/room/members/load.js
+++ b/src/matrix/room/members/load.js
@@ -18,7 +18,7 @@ limitations under the License.
 import {RoomMember} from "./RoomMember.js";
 
 async function loadMembers({roomId, storage}) {
-    const txn = await storage.readTxn([
+    const txn = storage.readTxn([
         storage.storeNames.roomMembers,
     ]);
     const memberDatas = await txn.roomMembers.getAll(roomId);
@@ -33,7 +33,7 @@ async function fetchMembers({summary, syncToken, roomId, hsApi, storage, setChan
     
     const memberResponse = await hsApi.members(roomId, {at: syncToken}).response();
 
-    const txn = await storage.readWriteTxn([
+    const txn = storage.readWriteTxn([
         storage.storeNames.roomSummary,
         storage.storeNames.roomMembers,
     ]);
diff --git a/src/matrix/room/sending/SendQueue.js b/src/matrix/room/sending/SendQueue.js
index 52c2e7b84d..eba5fcf3e2 100644
--- a/src/matrix/room/sending/SendQueue.js
+++ b/src/matrix/room/sending/SendQueue.js
@@ -48,6 +48,7 @@ export class SendQueue {
                 const pendingEvent = this._pendingEvents.get(this._amountSent);
                 console.log("trying to send", pendingEvent.content.body);
                 if (pendingEvent.remoteId) {
+                    this._amountSent += 1;
                     continue;
                 }
                 if (pendingEvent.needsEncryption) {
@@ -129,7 +130,7 @@ export class SendQueue {
     }
 
     async _tryUpdateEvent(pendingEvent) {
-        const txn = await this._storage.readWriteTxn([this._storage.storeNames.pendingEvents]);
+        const txn = this._storage.readWriteTxn([this._storage.storeNames.pendingEvents]);
         console.log("_tryUpdateEvent: got txn");
         try {
             // pendingEvent might have been removed already here
@@ -151,7 +152,7 @@ export class SendQueue {
 
     async _createAndStoreEvent(eventType, content) {
         console.log("_createAndStoreEvent");
-        const txn = await this._storage.readWriteTxn([this._storage.storeNames.pendingEvents]);
+        const txn = this._storage.readWriteTxn([this._storage.storeNames.pendingEvents]);
         let pendingEvent;
         try {
             const pendingEventsStore = txn.pendingEvents;
diff --git a/src/matrix/room/timeline/persistence/SyncWriter.js b/src/matrix/room/timeline/persistence/SyncWriter.js
index 7f2275b181..231f7295c0 100644
--- a/src/matrix/room/timeline/persistence/SyncWriter.js
+++ b/src/matrix/room/timeline/persistence/SyncWriter.js
@@ -104,6 +104,8 @@ export class SyncWriter {
             const memberChange = new MemberChange(this._roomId, event);
             const {member} = memberChange;
             if (member) {
+                // TODO: can we avoid writing redundant members here by checking
+                // if this is not a limited sync and the state is not in the timeline?
                 txn.roomMembers.set(member.serialize());
                 return memberChange;
             }
diff --git a/src/matrix/room/timeline/persistence/TimelineReader.js b/src/matrix/room/timeline/persistence/TimelineReader.js
index 37b15574f0..24ad4127e2 100644
--- a/src/matrix/room/timeline/persistence/TimelineReader.js
+++ b/src/matrix/room/timeline/persistence/TimelineReader.js
@@ -108,14 +108,14 @@ export class TimelineReader {
 
     readFrom(eventKey, direction, amount) {
         return new ReaderRequest(async r => {
-            const txn = await this._openTxn();
+            const txn = this._openTxn();
             return await this._readFrom(eventKey, direction, amount, r, txn);
         });
     }
 
     readFromEnd(amount) {
         return new ReaderRequest(async r => {
-            const txn = await this._openTxn();
+            const txn = this._openTxn();
             const liveFragment = await txn.timelineFragments.liveFragment(this._roomId);
             let entries;
             // room hasn't been synced yet
diff --git a/src/matrix/ssss/index.js b/src/matrix/ssss/index.js
index 286744fc20..d5bcfe9781 100644
--- a/src/matrix/ssss/index.js
+++ b/src/matrix/ssss/index.js
@@ -19,7 +19,7 @@ import {keyFromPassphrase} from "./passphrase.js";
 import {keyFromRecoveryKey} from "./recoveryKey.js";
 
 async function readDefaultKeyDescription(storage) {
-    const txn = await storage.readTxn([
+    const txn = storage.readTxn([
         storage.storeNames.accountData
     ]);
     const defaultKeyEvent = await txn.accountData.get("m.secret_storage.default_key");
diff --git a/src/matrix/storage/common.js b/src/matrix/storage/common.js
index 88238a111d..d96dc3597c 100644
--- a/src/matrix/storage/common.js
+++ b/src/matrix/storage/common.js
@@ -38,29 +38,12 @@ export const STORE_MAP = Object.freeze(STORE_NAMES.reduce((nameMap, name) => {
 }, {}));
 
 export class StorageError extends Error {
-    constructor(message, cause, value) {
-        let fullMessage = message;
-        if (cause) {
-            fullMessage += ": ";
-            if (typeof cause.name === "string") {
-                fullMessage += `(name: ${cause.name}) `;
-            }
-            if (typeof cause.code === "number") {
-                fullMessage += `(code: ${cause.code}) `;
-            }
-        }
-        if (value) {
-            fullMessage += `(value: ${JSON.stringify(value)}) `;
-        }
-        if (cause) {
-            fullMessage += cause.message;
-        }
-        super(fullMessage);
+    constructor(message, cause) {
+        super(message);
         if (cause) {
             this.errcode = cause.name;
         }
         this.cause = cause;
-        this.value = value;
     }
 
     get name() {
diff --git a/src/matrix/storage/idb/Storage.js b/src/matrix/storage/idb/Storage.js
index 9c79b92f05..03c2c8ef61 100644
--- a/src/matrix/storage/idb/Storage.js
+++ b/src/matrix/storage/idb/Storage.js
@@ -34,7 +34,7 @@ export class Storage {
         }
     }
 
-    async readTxn(storeNames) {
+    readTxn(storeNames) {
         this._validateStoreNames(storeNames);
         try {
             const txn = this._db.transaction(storeNames, "readonly");
@@ -44,7 +44,7 @@ export class Storage {
         }
     }
 
-    async readWriteTxn(storeNames) {
+    readWriteTxn(storeNames) {
         this._validateStoreNames(storeNames);
         try {
             const txn = this._db.transaction(storeNames, "readwrite");
diff --git a/src/matrix/storage/idb/Store.js b/src/matrix/storage/idb/Store.js
index a0ca0b9686..22851af04d 100644
--- a/src/matrix/storage/idb/Store.js
+++ b/src/matrix/storage/idb/Store.js
@@ -15,8 +15,15 @@ limitations under the License.
 */
 
 import {QueryTarget} from "./QueryTarget.js";
-import { reqAsPromise } from "./utils.js";
-import { StorageError } from "../common.js";
+import {IDBRequestAttemptError} from "./error.js";
+
+const LOG_REQUESTS = false;
+
+function logRequest(method, params, source) {
+    const storeName = source?.name;
+    const databaseName = source?.transaction?.db?.name;
+    console.info(`${databaseName}.${storeName}.${method}(${params.map(p => JSON.stringify(p)).join(", ")})`);
+}
 
 class QueryTargetWrapper {
     constructor(qt) {
@@ -36,62 +43,70 @@ class QueryTargetWrapper {
     }
     
     openKeyCursor(...params) {
-        // not supported on Edge 15
-        if (!this._qt.openKeyCursor) {
-            return this.openCursor(...params);
-        }
         try {
+            // not supported on Edge 15
+            if (!this._qt.openKeyCursor) {
+                LOG_REQUESTS && logRequest("openCursor", params, this._qt);
+                return this.openCursor(...params);
+            }
+            LOG_REQUESTS && logRequest("openKeyCursor", params, this._qt);
             return this._qt.openKeyCursor(...params);
         } catch(err) {
-            throw new StorageError("openKeyCursor failed", err);
+            throw new IDBRequestAttemptError("openKeyCursor", this._qt, err, params);
         }
     }
     
     openCursor(...params) {
         try {
+            LOG_REQUESTS && logRequest("openCursor", params, this._qt);
             return this._qt.openCursor(...params);
         } catch(err) {
-            throw new StorageError("openCursor failed", err);
+            throw new IDBRequestAttemptError("openCursor", this._qt, err, params);
         }
     }
 
     put(...params) {
         try {
+            LOG_REQUESTS && logRequest("put", params, this._qt);
             return this._qt.put(...params);
         } catch(err) {
-            throw new StorageError("put failed", err);
+            throw new IDBRequestAttemptError("put", this._qt, err, params);
         }
     }
 
     add(...params) {
         try {
+            LOG_REQUESTS && logRequest("add", params, this._qt);
             return this._qt.add(...params);
         } catch(err) {
-            throw new StorageError("add failed", err);
+            throw new IDBRequestAttemptError("add", this._qt, err, params);
         }
     }
 
     get(...params) {
         try {
+            LOG_REQUESTS && logRequest("get", params, this._qt);
             return this._qt.get(...params);
         } catch(err) {
-            throw new StorageError("get failed", err);
+            throw new IDBRequestAttemptError("get", this._qt, err, params);
         }
     }
     
     getKey(...params) {
         try {
+            LOG_REQUESTS && logRequest("getKey", params, this._qt);
             return this._qt.getKey(...params);
         } catch(err) {
-            throw new StorageError("getKey failed", err);
+            throw new IDBRequestAttemptError("getKey", this._qt, err, params);
         }
     }
 
     delete(...params) {
         try {
+            LOG_REQUESTS && logRequest("delete", params, this._qt);
             return this._qt.delete(...params);
         } catch(err) {
-            throw new StorageError("delete failed", err);
+            throw new IDBRequestAttemptError("delete", this._qt, err, params);
         }
     }
 
@@ -99,14 +114,16 @@ class QueryTargetWrapper {
         try {
             return this._qt.index(...params);
         } catch(err) {
-            throw new StorageError("index failed", err);
+            // TODO: map to different error? this is not a request
+            throw new IDBRequestAttemptError("index", this._qt, err, params);
         }
     }
 }
 
 export class Store extends QueryTarget {
-    constructor(idbStore) {
+    constructor(idbStore, transaction) {
         super(new QueryTargetWrapper(idbStore));
+        this._transaction = transaction;
     }
 
     get _idbStore() {
@@ -117,31 +134,27 @@ export class Store extends QueryTarget {
         return new QueryTarget(new QueryTargetWrapper(this._idbStore.index(indexName)));
     }
 
-    async put(value) {
-        try {
-            return await reqAsPromise(this._idbStore.put(value));
-        } catch(err) {
-            const originalErr = err.cause;
-            throw new StorageError(`put on ${err.databaseName}.${err.storeName} failed`, originalErr, value);
-        }
+    put(value) {
+        // If this request fails, the error will bubble up to the transaction and abort it,
+        // which is the behaviour we want. Therefore, it is ok to not create a promise for this
+        // request and await it.
+        // 
+        // Perhaps at some later point, we will want to handle an error (like ConstraintError) for
+        // individual write requests. In that case, we should add a method that returns a promise (e.g. putAndObserve)
+        // and call preventDefault on the event to prevent it from aborting the transaction
+        // 
+        // Note that this can still throw synchronously, like it does for TransactionInactiveError,
+        // see https://www.w3.org/TR/IndexedDB-2/#transaction-lifetime-concept
+        this._idbStore.put(value);
     }
 
-    async add(value) {
-        try {
-            return await reqAsPromise(this._idbStore.add(value));
-        } catch(err) {
-            const originalErr = err.cause;
-            throw new StorageError(`add on ${err.databaseName}.${err.storeName} failed`, originalErr, value);
-        }
+    add(value) {
+        // ok to not monitor result of request, see comment in `put`.
+        this._idbStore.add(value);
     }
 
-    async delete(keyOrKeyRange) {
-        try {
-            return await reqAsPromise(this._idbStore.delete(keyOrKeyRange));
-        } catch(err) {
-            const originalErr = err.cause;
-            throw new StorageError(`delete on ${err.databaseName}.${err.storeName} failed`, originalErr, keyOrKeyRange);
-        }
-        
+    delete(keyOrKeyRange) {
+        // ok to not monitor result of request, see comment in `put`.
+        this._idbStore.delete(keyOrKeyRange);
     }
 }
diff --git a/src/matrix/storage/idb/error.js b/src/matrix/storage/idb/error.js
new file mode 100644
index 0000000000..05390beab2
--- /dev/null
+++ b/src/matrix/storage/idb/error.js
@@ -0,0 +1,55 @@
+/*
+Copyright 2020 Bruno Windels <bruno@windels.cloud>
+Copyright 2020 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { StorageError } from "../common.js";
+
+export class IDBError extends StorageError {
+    constructor(message, source, cause) {
+        const storeName = source?.name || "<unknown store>";
+        const databaseName = source?.transaction?.db?.name || "<unknown db>";
+        let fullMessage = `${message} on ${databaseName}.${storeName}`;
+        if (cause) {
+            fullMessage += ": ";
+            if (typeof cause.name === "string") {
+                fullMessage += `(name: ${cause.name}) `;
+            }
+            if (typeof cause.code === "number") {
+                fullMessage += `(code: ${cause.code}) `;
+            }
+        }
+        if (cause) {
+            fullMessage += cause.message;
+        }
+        super(fullMessage, cause);
+        this.storeName = storeName;
+        this.databaseName = databaseName;
+    }
+}
+
+export class IDBRequestError extends IDBError {
+    constructor(request, message = "IDBRequest failed") {
+        const source = request?.source;
+        const cause = request.error;
+        super(message, source, cause);
+    }
+}
+
+export class IDBRequestAttemptError extends IDBError {
+    constructor(method, source, cause, params) {
+        super(`${method}(${params.map(p => JSON.stringify(p)).join(", ")}) failed`, source, cause);
+    }
+}
diff --git a/src/matrix/storage/idb/stores/PendingEventStore.js b/src/matrix/storage/idb/stores/PendingEventStore.js
index 0089831159..59b79a0569 100644
--- a/src/matrix/storage/idb/stores/PendingEventStore.js
+++ b/src/matrix/storage/idb/stores/PendingEventStore.js
@@ -58,11 +58,11 @@ export class PendingEventStore {
     
     add(pendingEvent) {
         pendingEvent.key = encodeKey(pendingEvent.roomId, pendingEvent.queueIndex);
-        return this._eventStore.add(pendingEvent);
+        this._eventStore.add(pendingEvent);
     }
 
     update(pendingEvent) {
-        return this._eventStore.put(pendingEvent);
+        this._eventStore.put(pendingEvent);
     }
 
     getAll() {
diff --git a/src/matrix/storage/idb/stores/SessionStore.js b/src/matrix/storage/idb/stores/SessionStore.js
index c6486651f6..3be8e87502 100644
--- a/src/matrix/storage/idb/stores/SessionStore.js
+++ b/src/matrix/storage/idb/stores/SessionStore.js
@@ -27,11 +27,11 @@ export class SessionStore {
 	}
 
 	set(key, value) {
-		return this._sessionStore.put({key, value});
+		this._sessionStore.put({key, value});
 	}
 
     add(key, value) {
-        return this._sessionStore.add({key, value});
+        this._sessionStore.add({key, value});
     }
 
     remove(key) {
diff --git a/src/matrix/storage/idb/stores/TimelineEventStore.js b/src/matrix/storage/idb/stores/TimelineEventStore.js
index a3a829f9ee..b7712337e7 100644
--- a/src/matrix/storage/idb/stores/TimelineEventStore.js
+++ b/src/matrix/storage/idb/stores/TimelineEventStore.js
@@ -238,7 +238,7 @@ export class TimelineEventStore {
         entry.key = encodeKey(entry.roomId, entry.fragmentId, entry.eventIndex);
         entry.eventIdKey = encodeEventIdKey(entry.roomId, entry.event.event_id);
         // TODO: map error? or in idb/store?
-        return this._timelineStore.add(entry);
+        this._timelineStore.add(entry);
     }
 
     /** Updates the entry into the store with the given [roomId, eventKey] combination.
@@ -247,17 +247,12 @@ export class TimelineEventStore {
      *  @return {Promise<>} a promise resolving to undefined if the operation was successful, or a StorageError if not.
      */
     update(entry) {
-        return this._timelineStore.put(entry);
+        this._timelineStore.put(entry);
     }
 
     get(roomId, eventKey) {
         return this._timelineStore.get(encodeKey(roomId, eventKey.fragmentId, eventKey.eventIndex));
     }
-    // returns the entries as well!! (or not always needed? I guess not always needed, so extra method)
-    removeRange(roomId, range) {
-        // TODO: read the entries!
-        return this._timelineStore.delete(range.asIDBKeyRange(roomId));
-    }
 
     getByEventId(roomId, eventId) {
         return this._timelineStore.index("byEventId").get(encodeEventIdKey(roomId, eventId));
diff --git a/src/matrix/storage/idb/stores/TimelineFragmentStore.js b/src/matrix/storage/idb/stores/TimelineFragmentStore.js
index 2a28c7bce5..849e52043a 100644
--- a/src/matrix/storage/idb/stores/TimelineFragmentStore.js
+++ b/src/matrix/storage/idb/stores/TimelineFragmentStore.js
@@ -62,11 +62,11 @@ export class TimelineFragmentStore {
     // like give them meaning depending on range. not for now probably ...
     add(fragment) {
         fragment.key = encodeKey(fragment.roomId, fragment.id);
-        return this._store.add(fragment);
+        this._store.add(fragment);
     }
 
     update(fragment) {
-        return this._store.put(fragment);
+        this._store.put(fragment);
     }
 
     get(roomId, fragmentId) {
diff --git a/src/matrix/storage/idb/utils.js b/src/matrix/storage/idb/utils.js
index adecba52c0..ac9f39110d 100644
--- a/src/matrix/storage/idb/utils.js
+++ b/src/matrix/storage/idb/utils.js
@@ -15,6 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+import { IDBRequestError } from "./error.js";
 import { StorageError } from "../common.js";
 
 let needsSyncPromise = false;
@@ -47,17 +48,6 @@ export async function checkNeedsSyncPromise() {
     return needsSyncPromise;
 }
 
-class IDBRequestError extends StorageError {
-    constructor(request) {
-        const source = request?.source;
-        const storeName = source?.name || "<unknown store>";
-        const databaseName = source?.transaction?.db?.name || "<unknown db>";
-        super(`Failed IDBRequest on ${databaseName}.${storeName}`, request.error);
-        this.storeName = storeName;
-        this.databaseName = databaseName;
-    }
-}
-
 // storage keys are defined to be unsigned 32bit numbers in WebPlatform.js, which is assumed by idb
 export function encodeUint32(n) {
     const hex = n.toString(16);
@@ -161,17 +151,6 @@ export async function select(db, storeName, toCursor, isDone) {
     return await fetchResults(cursor, isDone);
 }
 
-export async function updateSingletonStore(db, storeName, value) {
-    const tx = db.transaction([storeName], "readwrite");
-    const store = tx.objectStore(storeName);
-    const cursor = await reqAsPromise(store.openCursor());
-    if (cursor) {
-        return reqAsPromise(cursor.update(storeName));
-    } else {
-        return reqAsPromise(store.add(value));
-    }
-}
-
 export async function findStoreValue(db, storeName, toCursor, matchesValue) {
     if (!matchesValue) {
         matchesValue = () => true;
diff --git a/src/matrix/storage/memory/stores/RoomTimelineStore.js b/src/matrix/storage/memory/stores/RoomTimelineStore.js
index 5cc3117398..5be20eae13 100644
--- a/src/matrix/storage/memory/stores/RoomTimelineStore.js
+++ b/src/matrix/storage/memory/stores/RoomTimelineStore.js
@@ -234,11 +234,4 @@ export class RoomTimelineStore extends Store {
         const event = count ? this._timeline[startIndex] : undefined;
         return Promise.resolve(event);
     }
-
-    removeRange(roomId, range) {
-        this.assertWritable();
-        const {startIndex, count} = range.project(roomId);
-        const removedEntries = this._timeline.splice(startIndex, count);
-        return Promise.resolve(removedEntries);
-    }
 }