> It is the worst possible way to schedule jobs at scale.

The literal evidence proves that this approach is absolutely workable at scale, so “the worst possible way” clearly doesn’t apply.

The interesting question here is “how did they make this work?” The answer to which is immensely valuable to the technical community at large. “What are they building next?”, whilst interesting, is less immediately valuable as they will be building something Slack-scale, and most orgs are not Slack or Slack-scale