doc: Clarify supported features (#1090)

akka · Mar 28, 2024 · e264d0f · e264d0f
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diff --git a/docs/src/main/paradox/cleanup.md b/docs/src/main/paradox/cleanup.md
@@ -1,11 +1,5 @@
 # Database Cleanup
 
-@@@ warning
-
-When running any operation for a persistence id the actor with that persistence id must not be running!
-
-@@@
-
 If possible, it is best to keep all events in an event sourced system. That way new [projections](https://doc.akka.io/docs/akka-projection/current/index.html) 
 and the `tag_view` table can be re-built if it is corrupted (e.g. due to a two persistence ids writing events from two nodes in a split brain).
 
@@ -21,6 +15,15 @@ The @apidoc[akka.persistence.cassandra.cleanup.Cleanup] tool can retrospectively
 
 The cleanup tool can be combined with the @ref[query plugin](./read-journal.md) which has a query to get all persistence ids.
 
+@@@ warning
+
+When running an operation with `Cleanup` that deletes all events for a persistence id,
+the actor with that persistence id must not be running! If the actor is restarted it would in that
+case be recovered to the wrong state since the stored events have been deleted. Delete events before
+snapshot can still be used while the actor is running.
+
+@@@
+
 
 Scala
 : @@snip [snapshot-keyspace](/docs/src/test/scala/doc/cleanup/CleanupDocExample.scala) { #cleanup } 

diff --git a/docs/src/main/paradox/overview.md b/docs/src/main/paradox/overview.md
@@ -45,6 +45,25 @@ The table below shows Akka Persistence Cassandra’s direct dependencies and the
 
 To use the plugin with **Akka 2.5.x** you must use @extref:[version 0.103](apc-0.x:) or later in the 0.x series. 
 
+## Supported features
+
+Be aware of that many of the new features of [Akka Distributed Cluster](https://doc.akka.io/docs/akka-distributed-cluster/current/)
+and [Akka Edge](https://doc.akka.io/docs/akka-edge/current/) are only implemented by the
+[Akka Persistence R2DBC plugin](https://doc.akka.io/docs/akka-persistence-r2dbc/current/) and are not supported by the
+Cassandra plugin.
+
+Those features were developed for Distributed Cluster and Edge, but they are also useful in other contexts.
+Example of concrete features not supported by the Cassandra plugin: 
+
+* `eventsBySlices` query
+* Projections over gRPC
+* Replicated Event Sourcing over gRPC
+* Dynamic scaling of number of Projection instances
+* Low latency Projections
+* Projections starting from snapshots
+* Scalability of many Projections
+* Durable State entities
+
 ## History
 
 This [Apache Cassandra](https://cassandra.apache.org/) plugin to Akka Persistence was initiated [originally](https://github.com/krasserm/akka-persistence-cassandra) by Martin Krasser, [@krasserm](https://github.com/krasserm) in 2014.