One db that could be interesting here is CrateDB. It's a Lucene based DB that supports the postgres wire protocol. So you can run SQL queries against it.
I've tried figuring out if it supports acting as a pg read-replica, which sounds to me like the ideal set up - but it doesn't seem to be supported.
I have no affiliation to them, just met the team at an event and thought it sounded cool.
One of the ParadeDB maintainers here -- Being PostgreSQL wire protocol compatible is very different from being built inside Postgres on top of the Postgres pages, which is what ParadeDB does. You still need the "T" in ETL, e.g. transforming data from your source into the format of the sink (in your example CrateDB). This is where ETL costs and brittleness come into play.
So, I'm not versed enough in legal matters to be certain about this, so I tend to fallback to caution, but (A) customers I've worked with in the past seem to be wary of such copyleft licenses and (B) the contagious nature of such license would make me think twice about using it in a project of my own as well.
It would be nice to have such notion challenged but I'm not sure what would change my mind.
I would expect that most commercial companies that use Grafana would obtain a commercial license?
I've tried figuring out if it supports acting as a pg read-replica, which sounds to me like the ideal set up - but it doesn't seem to be supported.
I have no affiliation to them, just met the team at an event and thought it sounded cool.