For anyone looking for fast ci, I'd highly recommend webapp.io. it automatically caches layers if it detects it doesn't need to be run, and you can split a VM to shard test execution. Runs way faster than GitHub actions, you can ssh into any layer to debug, and it's just like a Linux machine/dockerfiles so no crazy syntax/mental model to learn. Support is great and we've been super happy with the experience. Best CI platform I've used by far.