diff --git a/gcloud-java-datastore/README.md b/gcloud-java-datastore/README.md
index de025d726721..aeaae2b621c6 100644
--- a/gcloud-java-datastore/README.md
+++ b/gcloud-java-datastore/README.md
@@ -128,6 +128,8 @@ while (results.hasNext()) {
 }
 ```
 
+Cloud Datastore relies on indexing to run queries. Indexing is turned on by default for most types of properties. To read more about indexing, see the [Cloud Datastore Index Configuration documentation](https://cloud.google.com/datastore/docs/tools/indexconfig).
+
 #### Complete source code
 
 Here we put together all the code shown above into one program.  This program assumes that you are running on Compute Engine or from your own desktop. To run this example on App Engine, simply move the code from the main method to your application's servlet class.
diff --git a/gcloud-java-datastore/src/main/java/com/google/gcloud/datastore/Query.java b/gcloud-java-datastore/src/main/java/com/google/gcloud/datastore/Query.java
index 343535d94628..5791d37e9426 100644
--- a/gcloud-java-datastore/src/main/java/com/google/gcloud/datastore/Query.java
+++ b/gcloud-java-datastore/src/main/java/com/google/gcloud/datastore/Query.java
@@ -35,6 +35,10 @@
  * A Google Cloud Datastore query.
  * For usage examples see {@link GqlQuery} and {@link StructuredQuery}.
  *
+ * Note that queries require proper indexing. See
+ * <a href="https://cloud.google.com/datastore/docs/tools/indexconfig">
+ * Cloud Datastore Index Configuration</a> for help configuring indexes.
+ *
  * @param <V> the type of the values returned by this query.
  * @see <a href="https://cloud.google.com/datastore/docs/concepts/queries">Datastore Queries</a>
  */