Add state store cache proposal - first draft

[berndverst]

Signed-off-by: Bernd Verst 4535280+berndverst@users.noreply.github.com

This is a proposal for using existing state stores with TTL feature as a cache layer for all state stores.

For example Redis Cache or In Memory state store could be used as caches for any other state store (e.g. Azure Cosmos DB)

[ItalyPaleAle]

I think this is a valid proposal, but wondering if we can make the API generic so that they can be used as a general-purpose cache too? Just like secret stores, which can be used as general purpose secret stores and for storing component secrets.

I also would recommend two more changes in components:

• Change the "in-memory" state store to be "production ready" rather than "developer-only" here: https://docs.dapr.io/reference/components-reference/supported-state-stores/
• Consider creating a "local FS" state store which stores data in the local filesystem (will have to be a volume mounted in the container)

[omidb]

Dapr sidecar has access to the lifecycle of a service (grpc (proxy) or http) and on each invoke we can cache the results for that specific request. This way we get a consistent cache for the service. We can invalidate the cache as soon as sidecar is restarted.

[berndverst]

Someone else please continue this proposal as I will not be active on it.