The Slick API is built on the Python framework FastAPI. FastAPI is async from the ground-up to ensure non-blocking on requests. Here's a nice blog post here where you can read more about FastAPI.
Slick is hosted on Google Cloud. The API and Database autoscale nearly infinitely. We also use some serverless functions for backend workflows and processing which will behave the same way.
Slick will always move quickly with feature development, but aim to never to break your integration. Although we are yet to version our API, if you are on any given version, our goal is to never release a breaking change to a given version - unless we need to for security reasons, feature requests or if we decide we no longer want to maintain it at some point in time. If that happens, we'll let you know.
Our public status page is under construction, but we monitor Slick constantly internally.