Postgres LISTEN/NOTIFY does not scale

I like this article. Lots of comments are stating that they are "using it wrong" and I'm sure they are. However, it does help to contrast the much more common, "use Postgres for everything" type sentiment. It is pretty hard to use Postgres wrong for relational things in the sense that everyone knows about indexes and so on. But using something like L/N comes with a separate learning curve anyway - evidenced in this case by someone having to read comments in the Postgres source code itself. Then if it turns out that it cannot work for your situation it may be very hard to back away from as you may have tightly integrated it with your normal Postgres stuff.

I've landed on Postgres/ClickHouse/NATS since together they handle nearly any conceivable workload managing relational, columnar, messaging/streaming very well. It is also not painful at all to use as it is lightweight and fast/easy to spin up in a simple docker compose. Postgres is of course the core and you don't always need all three but compliment each other very well imo. This has been my "go to" for a while.

This kind of issue always comes up when people put business logic inside the database. Databases are for data. The data goes in and the data goes out, but the data does not get to decide what happens next based on itself. That's what application code is for.

So what are your thoughts on constraints then? Foreign keys? Should that only be handled by the application, like Rails does (or did, haven't used in a long time).

Rails fully supports constraints and encourages you to use them.

You can either execute SQL in your migration or use add_check_constraint.