I got tired of the pricing and/or complexity of running message queues/event brokers, so decided to play around with implementing my own. It utilizes S3 as the source of truth, which makes it orders of magnitude easier to manage and cheaper to run. There's an ongoing blog series on the implementation: https://github.com/micvbang/simple-event-broker
I've had many use cases for using an event broker, but never found one that was simple enough that I would venture into hosting it myself, or cheap enough to rent/host that it was feasible. Once I realized that cloud object stores fit this problem perfectly (they provide durability and are cheap to use), I realized that it would be possible to write one myself. I wrote a post on it here, along with a tiny performance evaluation: https://blog.vbang.dk/2024/05/26/seb/
I spent the better part of a week working on it full time, but spread over months. I use it daily - it's serving the needs of multiple projects that I needed it for :)