Do you need separate systems when you already have Postgres?

I'll do you one better: do you really need Postgres and all these extensions when you already have a filesystem?

> only after pushing Postgres to its limits, documenting why it was insufficient, and accepting the operational cost of the alternative

I love Postgres as a DB but, really, this is ridiculous. No doubt these extensions can do the job well-enough but you might as well invest in learning the right tool for the problem from the start, when the stakes are still pretty low. Why wait until, ahem, Postgres is pushed to the limit before you spin up a Redis cluster?

You don't get free opcost by using Postgres for everything. Arguably if you end up with a monolith of a database, you are paying a higher opcost (imagine if too much caching can affect all CRUD ops in your platform). Or you can manage a cluster of PG instances but that's no less complex---each plugin still comes with its own opcost!

No Silver Bullet, No Free Lunch, and all that. If your problem domain really warrants something outside of relational storage, you're gonna pay that complexity cost one way or another. You can't escape it by shoehorning everything in Postgres, fantastic as a DB as it is.

Do filesystems offer ACID guarantees though? Depending on the use case, something like sqlite might work better (or write to a CAS system like S3).

For smaller projects and locally, I'm running background services via a compose file... it's a few lines of configuration, and just works. Redis is crazy low hanging fruit.. even job queues that run over Redis make a bit more sense than with Postgres more often than not.

I'm far more hesitant to throw a more formal MQ in the mix though... mostly from experience in that a lot of mid level ("senior") developers don't really understand queues very well at all. Even if conceptually, using tables for queues is more complex.

That said, I will use PG for workflows similar to K/V, Document (JSONB) and other structures over reaching for say MongoDB, etc.

The reason for separate systems is that some of them go down. And by "go down", that includes you wanting to deploy a new version. Or restore from backup as the article suggested.

lets take it one step further: Do you really need Postgres when you already have SQLite?