Yea FLASH is only in the Enterprise version. At a rough level the open source is the best cache we can make while pro/enterprise is the best full featured database. It’s not fully there yet but the end goal is you can get caching and persistence in one place.
The FLASH feature in Enterprise can send all writes to disk before replying +OK, however notably we don’t fsync (AOF is still recommended if you need that). In these deployments it’s not necessary to use RDB or AOF except for replication.
And of course we have all the existing options already in Redis.
Someone on my team looked at it, and for our workload (lots of MGETs per query) it wasn't that much better than redis. We may still go with it though, our GCP Memorystore instance is pretty much at 100% CPU constantly.
Long running commands are still a problem. We have infrastructure in the Enterprise version to alleviate this but so far we’ve enabled it only for KEYS and SCAN. MGET does come up frequently so it’s on our radar.