(Disclaimer: Postgres guy, so I'm likely not impartial)

For read performance if your dataset fits in memory PG is just as fast as Redis.

The main attraction of Redis is in-memory writes with async persistence. Trading durability and availability for the increased performance. If you give up this then there is precisely 0 reasons to choose Redis over PostgreSQL.

FWIW, you can have that in postgres as well, cf. synchronous_commit = off

> Trading durability and availability for the increased performance. If you give up this then there is precisely 0 reasons to choose Redis over PostgreSQL.

As a PostgreSQL developer, I'd say that performance / latency / jitter can still be reasons to choose redis over postgres. The per-read overhead in redis is often a good bit lower than in postgres, and there's less variability in response times.

https://muut.com/blog/technology/redis-as-primary-datastore-...

Counter point of a real world implementation where they tried to make it the primary data store.

They resorted to weird hack-y shit for something I use MySQL or Postgres for on a regular basis. So have most people who built stuff on Redis like this:

> I use Redis as the primary and only database. > Additionally, it has data persistence reliability on par with Postgres and other battle-tested databases[0], so couldn't be happier about that.