That's what I meant by "no persistence needed". In both cases, I wasn't actually saving anything to disk. I needed an in-memory storage for a never-ending stream of incoming data that would be read (and purged) by a separate process, no biggie if the data got lost occasionally.

I also simply inserted and read the data, no complex queries or anything. Key-value store is all I needed and for this particular case PostgreSQL was as good at it as Redis.

Why did you use a database instead of just creating a global map and running in memory? Sharding?

No - different processes were reading and writing.

And once you implement a global map which is accessible from multiple processes, you might as well use an existing solution, like Redis. Or, as I've learned, pgSQL - which gave me the same performance with less moving parts (because I was already using it) when I disabled WAL.