Postgres can be used for columnar data, as a graph database (using https://github.com/bitnine-oss/agensgraph), as a timeseries database (using https://github.com/timescale/timescaledb), and as a KV store (which is astoundingly simple to do using its builtin jsonb column type)
In fact at this point the only thing other than Postgres I would look at is FoundationDB due to the fact that (although it takes some time) you can model and run ANY kind of data store on top of it.
Postgres can be used for columnar data, as a graph database (using https://github.com/bitnine-oss/agensgraph), as a timeseries database (using https://github.com/timescale/timescaledb), and as a KV store (which is astoundingly simple to do using its builtin jsonb column type)
In fact at this point the only thing other than Postgres I would look at is FoundationDB due to the fact that (although it takes some time) you can model and run ANY kind of data store on top of it.