- The service mentioned (now called https://webapp.io ) eventually made it into YC (S20) and still uses postgres as its pub/sub implementation, doing hundreds of thousands of messages per day. The postgres instance now runs on 32 cores and 128gb of memory and has scaled well.
- We bolstered Postgres's PUBLISH with Redis pub/sub for high traffic code paths, but it's been nice having ACID guarantees as the default for less popular paths (e.g., webhook handling)
- This pattern only ever caused one operational incident, where a transaction held a lock which caused the notification queue to start growing, and eventually (silently) stop sending messages, starting postgres with statement_timeout=(a few days) was enough to solve this
Previous discussion: https://news.ycombinator.com/item?id=21484215
Happy to answer any questions!
This is not much load at all, an iPhone running RabbitMQ could process many millions of messages per day. Even 1M messages per day is only 11 messages per second average. i.e. not taxing at all.
I find it amusing that we happily play these AAA gaming experiences that are totally fantastical in their ability to deal with millions of things per frame and then turn around and pretend like hundreds of thousands of things per day is some kind of virtue.