The library has no stack, it's just a set of plugins you can either use directly (Ruby, Elixir, Go) or with a framework (Rails, Sinatra, Phoenix, Ash, etc). They write into a database you already run. Setup is adding the plugin and pointing it at your DB. Redis, Postgres, MongoDB, MySQL or SQLite. As for when you would feel some load from it, it really depends on your volume. I would say somewhere around 100k+ events a day is where the load starts being noticeable. Until then I wouldn't worry much about extra load.

If you want to self-host the App, it's pretty lightweight. While it's an Elixir app and you could compile and run it yourself, it comes packaged as a Docker image and it has a Kubernetes/Helm deployment documented. You can either point it to your own Postgres or it will launch its own so it can hold some of its own data like users, dashboards, monitors, etc. For 2-3 users one instance is plenty and you can easily run that on 1 CPU and 2GB RAM. Double that if you want redundancy.

Good luck with deepsql!