NATS doesn't really have advanced query features though. It has a lot of really nice things, but advanced querying isn't one of them. Not to mention I don't know if NATS does well with large datasets, does it have sharding capability for it's KV and object stores?
I use NATS at work, and I have had the privilege to speak with some of the folks at Synadia about this stuff.
Re: advanced querying: the recommended way to do this is to build an index out of band (like Redis (or a fork) or SQLite or something) that references the stored messages by sequence number. By doing that, your index is just this ephemeral thing that can be dynamically built to exactly optimize for the queries you're using it for.
Re: sharding: no, it doesn't support simple sharding. You can achieve sharding by standing up multiple NATS instances, and making a new stream (KV and object store are also just streams) on each instance, and capture some subset of the stream on each instance. The client (or perhaps a service querying on behalf of the client) would have to me smart enough to be able to mux the sources together.
Does it handle clustering/redundancy for the data stored in KV/object store? My intuition says yes because I believe it supports it at the "node" level
