I wonder why they didn't evaluate at some point using an immutable infrastructure approach leveraging tools like Spinnaker to manage the deploy? They sure have the muscle and numbers to use it and even contribute to it actively, no? I mean, I know that deploying your software is usually something pretty tied to a specific engineering team but I really like the immutable approach and I was wondering why a company the size of Slack, born and grown in the "right" time, did not consider it.