Once you need something a bit more heavyweight than Travis (e.g. more CPU) I would highly suggest Buildkite (https://www.buildkite.com). It’s a “bring your own machines” solution, which means you can have beefy machines (e.g. via buildkite on EC2 spot autoscaling), or even machines that run inside production without handing buildkite itself any secrets. We’ve been using it at Ladder and it’s been phenomenal.

Also it has a lot of emojis.