diff --git a/exp/lighthorizon/index/backend/backend.go b/exp/lighthorizon/index/backend/backend.go
new file mode 100644
index 0000000000..580e5f4d6e
--- /dev/null
+++ b/exp/lighthorizon/index/backend/backend.go
@@ -0,0 +1,14 @@
+package index
+
+import types "github.com/stellar/go/exp/lighthorizon/index/types"
+
+// TODO: Use a more standardized filesystem-style backend, so we can re-use
+// code
+type Backend interface {
+	Flush(map[string]types.NamedIndices) error
+	FlushAccounts([]string) error
+	Read(account string) (types.NamedIndices, error)
+	ReadAccounts() ([]string, error)
+	FlushTransactions(map[string]*types.TrieIndex) error
+	ReadTransactions(prefix string) (*types.TrieIndex, error)
+}
diff --git a/exp/lighthorizon/index/file.go b/exp/lighthorizon/index/backend/file.go
similarity index 90%
rename from exp/lighthorizon/index/file.go
rename to exp/lighthorizon/index/backend/file.go
index 530c089582..dda1858cb8 100644
--- a/exp/lighthorizon/index/file.go
+++ b/exp/lighthorizon/index/backend/file.go
@@ -8,6 +8,7 @@ import (
 	"os"
 	"path/filepath"
 
+	types "github.com/stellar/go/exp/lighthorizon/index/types"
 	"github.com/stellar/go/support/errors"
 	"github.com/stellar/go/support/log"
 )
@@ -17,14 +18,6 @@ type FileBackend struct {
 	parallel uint32
 }
 
-func NewFileStore(dir string, parallel uint32) (Store, error) {
-	backend, err := NewFileBackend(dir, parallel)
-	if err != nil {
-		return nil, err
-	}
-	return NewStore(backend)
-}
-
 func NewFileBackend(dir string, parallel uint32) (*FileBackend, error) {
 	return &FileBackend{
 		dir:      dir,
@@ -32,7 +25,7 @@ func NewFileBackend(dir string, parallel uint32) (*FileBackend, error) {
 	}, nil
 }
 
-func (s *FileBackend) Flush(indexes map[string]map[string]*CheckpointIndex) error {
+func (s *FileBackend) Flush(indexes map[string]types.NamedIndices) error {
 	return parallelFlush(s.parallel, indexes, s.writeBatch)
 }
 
@@ -88,7 +81,7 @@ func (s *FileBackend) writeBatch(b *batch) error {
 	return nil
 }
 
-func (s *FileBackend) FlushTransactions(indexes map[string]*TrieIndex) error {
+func (s *FileBackend) FlushTransactions(indexes map[string]*types.TrieIndex) error {
 	// TODO: Parallelize this
 	for key, index := range indexes {
 		path := filepath.Join(s.dir, "tx", key)
@@ -125,7 +118,7 @@ func (s *FileBackend) FlushTransactions(indexes map[string]*TrieIndex) error {
 	return nil
 }
 
-func (s *FileBackend) Read(account string) (map[string]*CheckpointIndex, error) {
+func (s *FileBackend) Read(account string) (types.NamedIndices, error) {
 	log.Debugf("Opening index: %s", account)
 	b, err := os.Open(filepath.Join(s.dir, account[:3], account))
 	if err != nil {
@@ -185,7 +178,7 @@ func (s *FileBackend) ReadAccounts() ([]string, error) {
 	return accounts, nil
 }
 
-func (s *FileBackend) ReadTransactions(prefix string) (*TrieIndex, error) {
+func (s *FileBackend) ReadTransactions(prefix string) (*types.TrieIndex, error) {
 	log.Debugf("Opening index: %s", prefix)
 	b, err := os.Open(filepath.Join(s.dir, "tx", prefix))
 	if err != nil {
@@ -198,7 +191,7 @@ func (s *FileBackend) ReadTransactions(prefix string) (*TrieIndex, error) {
 		return nil, os.ErrNotExist
 	}
 	defer zr.Close()
-	var index TrieIndex
+	var index types.TrieIndex
 	_, err = index.ReadFrom(zr)
 	if err != nil {
 		log.Errorf("Unable to parse %s: %v", prefix, err)
diff --git a/exp/lighthorizon/index/file_test.go b/exp/lighthorizon/index/backend/file_test.go
similarity index 100%
rename from exp/lighthorizon/index/file_test.go
rename to exp/lighthorizon/index/backend/file_test.go
diff --git a/exp/lighthorizon/index/gzip.go b/exp/lighthorizon/index/backend/gzip.go
similarity index 73%
rename from exp/lighthorizon/index/gzip.go
rename to exp/lighthorizon/index/backend/gzip.go
index c2a272e1c9..37a0f41ac1 100644
--- a/exp/lighthorizon/index/gzip.go
+++ b/exp/lighthorizon/index/backend/gzip.go
@@ -4,9 +4,11 @@ import (
 	"bytes"
 	"compress/gzip"
 	"io"
+
+	types "github.com/stellar/go/exp/lighthorizon/index/types"
 )
 
-func writeGzippedTo(w io.Writer, indexes map[string]*CheckpointIndex) (int64, error) {
+func writeGzippedTo(w io.Writer, indexes types.NamedIndices) (int64, error) {
 	zw := gzip.NewWriter(w)
 
 	var n int64
@@ -28,12 +30,12 @@ func writeGzippedTo(w io.Writer, indexes map[string]*CheckpointIndex) (int64, er
 	return n, nil
 }
 
-func readGzippedFrom(r io.Reader) (map[string]*CheckpointIndex, int64, error) {
+func readGzippedFrom(r io.Reader) (types.NamedIndices, int64, error) {
 	zr, err := gzip.NewReader(r)
 	if err != nil {
 		return nil, 0, err
 	}
-	indexes := map[string]*CheckpointIndex{}
+	indexes := types.NamedIndices{}
 	var buf bytes.Buffer
 	var n int64
 	for {
@@ -45,7 +47,7 @@ func readGzippedFrom(r io.Reader) (map[string]*CheckpointIndex, int64, error) {
 			return nil, n, err
 		}
 
-		ind, err := NewCheckpointIndexFromBytes(buf.Bytes())
+		ind, err := types.NewCheckpointIndexFromBytes(buf.Bytes())
 		if err != nil {
 			return nil, n, err
 		}
diff --git a/exp/lighthorizon/index/gzip_test.go b/exp/lighthorizon/index/backend/gzip_test.go
similarity index 75%
rename from exp/lighthorizon/index/gzip_test.go
rename to exp/lighthorizon/index/backend/gzip_test.go
index 32058b07ee..6efbc8c5e8 100644
--- a/exp/lighthorizon/index/gzip_test.go
+++ b/exp/lighthorizon/index/backend/gzip_test.go
@@ -4,12 +4,13 @@ import (
 	"bytes"
 	"testing"
 
+	types "github.com/stellar/go/exp/lighthorizon/index/types"
 	"github.com/stretchr/testify/require"
 )
 
 func TestGzipWriteReadRoundtrip(t *testing.T) {
-	indexes := map[string]*CheckpointIndex{}
-	index := &CheckpointIndex{}
+	indexes := types.NamedIndices{}
+	index := &types.CheckpointIndex{}
 	index.SetActive(5)
 	indexes["A"] = index
 
diff --git a/exp/lighthorizon/index/parallel_flush.go b/exp/lighthorizon/index/backend/parallel_flush.go
similarity index 84%
rename from exp/lighthorizon/index/parallel_flush.go
rename to exp/lighthorizon/index/backend/parallel_flush.go
index 37b8bbb39e..4f9b14e783 100644
--- a/exp/lighthorizon/index/parallel_flush.go
+++ b/exp/lighthorizon/index/backend/parallel_flush.go
@@ -5,17 +5,18 @@ import (
 	"sync/atomic"
 	"time"
 
+	types "github.com/stellar/go/exp/lighthorizon/index/types"
 	"github.com/stellar/go/support/log"
 )
 
 type batch struct {
 	account string
-	indexes map[string]*CheckpointIndex
+	indexes types.NamedIndices
 }
 
 type flushBatch func(b *batch) error
 
-func parallelFlush(parallel uint32, allIndexes map[string]map[string]*CheckpointIndex, f flushBatch) error {
+func parallelFlush(parallel uint32, allIndexes map[string]types.NamedIndices, f flushBatch) error {
 	var wg sync.WaitGroup
 
 	batches := make(chan *batch, parallel)
diff --git a/exp/lighthorizon/index/s3.go b/exp/lighthorizon/index/backend/s3.go
similarity index 89%
rename from exp/lighthorizon/index/s3.go
rename to exp/lighthorizon/index/backend/s3.go
index f57fa4dfda..59df939596 100644
--- a/exp/lighthorizon/index/s3.go
+++ b/exp/lighthorizon/index/backend/s3.go
@@ -15,6 +15,8 @@ import (
 	"github.com/aws/aws-sdk-go/service/s3/s3manager"
 	"github.com/stellar/go/support/errors"
 	"github.com/stellar/go/support/log"
+
+	types "github.com/stellar/go/exp/lighthorizon/index/types"
 )
 
 const BUCKET = "horizon-index"
@@ -27,14 +29,6 @@ type S3Backend struct {
 	prefix     string
 }
 
-func NewS3Store(awsConfig *aws.Config, prefix string, parallel uint32) (Store, error) {
-	backend, err := NewS3Backend(awsConfig, prefix, parallel)
-	if err != nil {
-		return nil, err
-	}
-	return NewStore(backend)
-}
-
 func NewS3Backend(awsConfig *aws.Config, prefix string, parallel uint32) (*S3Backend, error) {
 	s3Session, err := session.NewSession(awsConfig)
 	if err != nil {
@@ -72,7 +66,7 @@ func (s *S3Backend) FlushAccounts(accounts []string) error {
 	return nil
 }
 
-func (s *S3Backend) Flush(indexes map[string]map[string]*CheckpointIndex) error {
+func (s *S3Backend) Flush(indexes map[string]types.NamedIndices) error {
 	return parallelFlush(s.parallel, indexes, s.writeBatch)
 }
 
@@ -98,7 +92,7 @@ func (s *S3Backend) writeBatch(b *batch) error {
 	return nil
 }
 
-func (s *S3Backend) FlushTransactions(indexes map[string]*TrieIndex) error {
+func (s *S3Backend) FlushTransactions(indexes map[string]*types.TrieIndex) error {
 	// TODO: Parallelize this
 	var buf bytes.Buffer
 	for key, index := range indexes {
@@ -156,7 +150,7 @@ func (s *S3Backend) path(account string) string {
 	return filepath.Join(s.prefix, account[:10], account)
 }
 
-func (s *S3Backend) Read(account string) (map[string]*CheckpointIndex, error) {
+func (s *S3Backend) Read(account string) (types.NamedIndices, error) {
 	// Check if index exists in S3
 	log.Debugf("Downloading index: %s", account)
 	var err error
@@ -179,7 +173,7 @@ func (s *S3Backend) Read(account string) (map[string]*CheckpointIndex, error) {
 		if n == 0 {
 			return nil, os.ErrNotExist
 		}
-		var indexes map[string]*CheckpointIndex
+		var indexes map[string]*types.CheckpointIndex
 		indexes, _, err = readGzippedFrom(bytes.NewReader(b.Bytes()))
 		if err != nil {
 			log.Errorf("Unable to parse %s: %v", account, err)
@@ -191,7 +185,7 @@ func (s *S3Backend) Read(account string) (map[string]*CheckpointIndex, error) {
 	return nil, err
 }
 
-func (s *S3Backend) ReadTransactions(prefix string) (*TrieIndex, error) {
+func (s *S3Backend) ReadTransactions(prefix string) (*types.TrieIndex, error) {
 	// Check if index exists in S3
 	log.Debugf("Downloading index: %s", prefix)
 	b := &aws.WriteAtBuffer{}
@@ -216,7 +210,7 @@ func (s *S3Backend) ReadTransactions(prefix string) (*TrieIndex, error) {
 	}
 	defer zr.Close()
 
-	var index TrieIndex
+	var index types.TrieIndex
 	_, err = index.ReadFrom(zr)
 	if err != nil {
 		log.Errorf("Unable to parse %s: %v", prefix, err)
diff --git a/exp/lighthorizon/index/cmd/batch/reduce/main.go b/exp/lighthorizon/index/cmd/batch/reduce/main.go
index 0fa871d38d..ac80ac932b 100644
--- a/exp/lighthorizon/index/cmd/batch/reduce/main.go
+++ b/exp/lighthorizon/index/cmd/batch/reduce/main.go
@@ -10,6 +10,7 @@ import (
 	"sync"
 
 	"github.com/stellar/go/exp/lighthorizon/index"
+	types "github.com/stellar/go/exp/lighthorizon/index/types"
 	"github.com/stellar/go/support/errors"
 	"github.com/stellar/go/support/log"
 )
@@ -337,7 +338,7 @@ func (cfg *ReduceConfig) shouldProcessTx(txPrefix byte, routineIndex uint32) boo
 
 // For every index that exists in `dest`, finds the corresponding index in
 // `source` and merges it into `dest`'s version.
-func mergeIndices(dest, source map[string]*index.CheckpointIndex) error {
+func mergeIndices(dest, source map[string]*types.CheckpointIndex) error {
 	for name, index := range dest {
 		// The source doesn't contain this particular index.
 		//
diff --git a/exp/lighthorizon/index/connect.go b/exp/lighthorizon/index/connect.go
index 4620046f29..cc0a9dd4b0 100644
--- a/exp/lighthorizon/index/connect.go
+++ b/exp/lighthorizon/index/connect.go
@@ -6,6 +6,8 @@ import (
 	"path/filepath"
 
 	"github.com/aws/aws-sdk-go/aws"
+
+	backend "github.com/stellar/go/exp/lighthorizon/index/backend"
 )
 
 func Connect(backendUrl string) (Store, error) {
@@ -31,3 +33,19 @@ func Connect(backendUrl string) (Store, error) {
 			parsed.Scheme, backendUrl)
 	}
 }
+
+func NewFileStore(dir string, parallel uint32) (Store, error) {
+	backend, err := backend.NewFileBackend(dir, parallel)
+	if err != nil {
+		return nil, err
+	}
+	return NewStore(backend)
+}
+
+func NewS3Store(awsConfig *aws.Config, prefix string, parallel uint32) (Store, error) {
+	backend, err := backend.NewS3Backend(awsConfig, prefix, parallel)
+	if err != nil {
+		return nil, err
+	}
+	return NewStore(backend)
+}
diff --git a/exp/lighthorizon/index/store.go b/exp/lighthorizon/index/store.go
index 640af10f76..a36e60ec6e 100644
--- a/exp/lighthorizon/index/store.go
+++ b/exp/lighthorizon/index/store.go
@@ -6,6 +6,9 @@ import (
 	"io"
 	"os"
 	"sync"
+
+	backend "github.com/stellar/go/exp/lighthorizon/index/backend"
+	types "github.com/stellar/go/exp/lighthorizon/index/types"
 )
 
 type Store interface {
@@ -14,37 +17,26 @@ type Store interface {
 	TransactionTOID(hash [32]byte) (int64, error)
 	AddParticipantsToIndexes(checkpoint uint32, index string, participants []string) error
 	AddParticipantsToIndexesNoBackend(checkpoint uint32, index string, participants []string) error
-	AddParticipantToIndexesNoBackend(participant string, indexes map[string]*CheckpointIndex)
+	AddParticipantToIndexesNoBackend(participant string, indexes types.NamedIndices)
 	Flush() error
 	FlushAccounts() error
-	Read(account string) (map[string]*CheckpointIndex, error)
-	ReadAccounts() ([]string, error)
-	ReadTransactions(prefix string) (*TrieIndex, error)
-	MergeTransactions(prefix string, other *TrieIndex) error
-}
-
-// TODO: Use a more standardized filesystem-style backend, so we can re-use
-// code
-type Backend interface {
-	Flush(map[string]map[string]*CheckpointIndex) error
-	FlushAccounts([]string) error
-	Read(account string) (map[string]*CheckpointIndex, error)
+	Read(account string) (types.NamedIndices, error)
 	ReadAccounts() ([]string, error)
-	FlushTransactions(map[string]*TrieIndex) error
-	ReadTransactions(prefix string) (*TrieIndex, error)
+	ReadTransactions(prefix string) (*types.TrieIndex, error)
+	MergeTransactions(prefix string, other *types.TrieIndex) error
 }
 
 type store struct {
 	mutex     sync.RWMutex
-	indexes   map[string]map[string]*CheckpointIndex
-	txIndexes map[string]*TrieIndex
-	backend   Backend
+	indexes   map[string]types.NamedIndices
+	txIndexes map[string]*types.TrieIndex
+	backend   backend.Backend
 }
 
-func NewStore(backend Backend) (Store, error) {
+func NewStore(backend backend.Backend) (Store, error) {
 	return &store{
-		indexes:   map[string]map[string]*CheckpointIndex{},
-		txIndexes: map[string]*TrieIndex{},
+		indexes:   map[string]types.NamedIndices{},
+		txIndexes: map[string]*types.TrieIndex{},
 		backend:   backend,
 	}, nil
 }
@@ -63,7 +55,7 @@ func (s *store) FlushAccounts() error {
 	return s.backend.FlushAccounts(s.accounts())
 }
 
-func (s *store) Read(account string) (map[string]*CheckpointIndex, error) {
+func (s *store) Read(account string) (types.NamedIndices, error) {
 	return s.backend.Read(account)
 }
 
@@ -71,11 +63,11 @@ func (s *store) ReadAccounts() ([]string, error) {
 	return s.backend.ReadAccounts()
 }
 
-func (s *store) ReadTransactions(prefix string) (*TrieIndex, error) {
+func (s *store) ReadTransactions(prefix string) (*types.TrieIndex, error) {
 	return s.getCreateTrieIndex(prefix)
 }
 
-func (s *store) MergeTransactions(prefix string, other *TrieIndex) error {
+func (s *store) MergeTransactions(prefix string, other *types.TrieIndex) error {
 	index, err := s.getCreateTrieIndex(prefix)
 	if err != nil {
 		return err
@@ -103,12 +95,12 @@ func (s *store) Flush() error {
 	}
 
 	// clear indexes to save memory
-	s.indexes = map[string]map[string]*CheckpointIndex{}
+	s.indexes = map[string]types.NamedIndices{}
 
 	if err := s.backend.FlushTransactions(s.txIndexes); err != nil {
 		return err
 	}
-	s.txIndexes = map[string]*TrieIndex{}
+	s.txIndexes = map[string]*types.TrieIndex{}
 
 	return nil
 }
@@ -147,12 +139,12 @@ func (s *store) AddParticipantsToIndexesNoBackend(checkpoint uint32, index strin
 	for _, participant := range participants {
 		_, ok := s.indexes[participant]
 		if !ok {
-			s.indexes[participant] = map[string]*CheckpointIndex{}
+			s.indexes[participant] = map[string]*types.CheckpointIndex{}
 		}
 
 		ind, ok := s.indexes[participant][index]
 		if !ok {
-			ind = &CheckpointIndex{}
+			ind = &types.CheckpointIndex{}
 			s.indexes[participant][index] = ind
 		}
 
@@ -165,7 +157,7 @@ func (s *store) AddParticipantsToIndexesNoBackend(checkpoint uint32, index strin
 	return nil
 }
 
-func (s *store) AddParticipantToIndexesNoBackend(participant string, indexes map[string]*CheckpointIndex) {
+func (s *store) AddParticipantToIndexesNoBackend(participant string, indexes types.NamedIndices) {
 	s.mutex.Lock()
 	defer s.mutex.Unlock()
 	s.indexes[participant] = indexes
@@ -185,14 +177,14 @@ func (s *store) AddParticipantsToIndexes(checkpoint uint32, index string, partic
 	return nil
 }
 
-func (s *store) getCreateIndex(account, id string) (*CheckpointIndex, error) {
+func (s *store) getCreateIndex(account, id string) (*types.CheckpointIndex, error) {
 	s.mutex.Lock()
 	defer s.mutex.Unlock()
 
 	// Check if we already have it loaded
 	accountIndexes, ok := s.indexes[account]
 	if !ok {
-		accountIndexes = map[string]*CheckpointIndex{}
+		accountIndexes = types.NamedIndices{}
 	}
 	ind, ok := accountIndexes[id]
 	if ok {
@@ -210,7 +202,7 @@ func (s *store) getCreateIndex(account, id string) (*CheckpointIndex, error) {
 	ind, ok = accountIndexes[id]
 	if !ok {
 		// Not found anywhere, make a new one.
-		ind = &CheckpointIndex{}
+		ind = &types.CheckpointIndex{}
 		accountIndexes[id] = ind
 	}
 	s.indexes[account] = accountIndexes
@@ -226,7 +218,7 @@ func (s *store) NextActive(account, indexId string, afterCheckpoint uint32) (uin
 	return ind.NextActive(afterCheckpoint)
 }
 
-func (s *store) getCreateTrieIndex(prefix string) (*TrieIndex, error) {
+func (s *store) getCreateTrieIndex(prefix string) (*types.TrieIndex, error) {
 	s.mutex.Lock()
 	defer s.mutex.Unlock()
 
@@ -247,7 +239,7 @@ func (s *store) getCreateTrieIndex(prefix string) (*TrieIndex, error) {
 	index, ok = s.txIndexes[prefix]
 	if !ok {
 		// Not found anywhere, make a new one.
-		index = &TrieIndex{}
+		index = &types.TrieIndex{}
 		s.txIndexes[prefix] = index
 	}
 
diff --git a/exp/lighthorizon/index/main.go b/exp/lighthorizon/index/types/bitmap.go
similarity index 99%
rename from exp/lighthorizon/index/main.go
rename to exp/lighthorizon/index/types/bitmap.go
index a14713b37a..a3446c9bf3 100644
--- a/exp/lighthorizon/index/main.go
+++ b/exp/lighthorizon/index/types/bitmap.go
@@ -17,6 +17,8 @@ type CheckpointIndex struct {
 	lastCheckpoint  uint32
 }
 
+type NamedIndices map[string]*CheckpointIndex
+
 func NewCheckpointIndexFromBytes(b []byte) (*CheckpointIndex, error) {
 	xdrCheckpoint := xdr.CheckpointIndex{}
 	err := xdrCheckpoint.UnmarshalBinary(b)
diff --git a/exp/lighthorizon/index/main_test.go b/exp/lighthorizon/index/types/bitmap_test.go
similarity index 100%
rename from exp/lighthorizon/index/main_test.go
rename to exp/lighthorizon/index/types/bitmap_test.go
diff --git a/exp/lighthorizon/index/trie.go b/exp/lighthorizon/index/types/trie.go
similarity index 100%
rename from exp/lighthorizon/index/trie.go
rename to exp/lighthorizon/index/types/trie.go
diff --git a/exp/lighthorizon/index/trie_test.go b/exp/lighthorizon/index/types/trie_test.go
similarity index 100%
rename from exp/lighthorizon/index/trie_test.go
rename to exp/lighthorizon/index/types/trie_test.go