I have a use case that is pretty perfect for Akka Cluster Sharding except for one thing. Each entity will have a string as part of its state, and while almost all the application needs can be accomplished by maintaining that state, there is also a need to search the collection of entities by those strings - think autocomplete given substrings, where the persistenceId is the information that would be returned.
I am curious how other people have combined akka cluster sharding with searching, where you are searching by a field that would normally be part of the state of the actor. It seems the alternatives are:
Use a separate horizontally scalable repository that can be queried, like cassandra, that will associate these strings with the persistence ids for the actors/entities. This would require each actor to write to the repository when the relevant part of its state gets updated. (Not the same as using akka persistence as it would be a different repository schema.)
Write a custom layer to query the akka persistence schema directly, although this seems improper, and impractical anyway given how the serialized events and snapshots are stored.
Integrate a distributed in-memory cache (probably backed with some persistence repository) where you can search by value, that integrates well with akka, if there is anything like this.
I checked to see if Distributed Data would be a fit, but I wasn’t sure if that worked well for searching by value, plus I think this would involve more records than DD is a good fit for anyway.
Any suggestions? It seems like it would be a pretty common need to search among entities in a cluster.