[andrewaylett]

There's continuous, and then there's continuous. Where I work (which is easy enough to find out if you're curious, and the same order of magnitude size of engineering team as Slack) we deploy hundreds of times a day. But that's because our units of deployment are small (and target-specific, so a single logical change can trigger multiple logical deployments). So we're not deploying the same thing hundreds of times per day, we're deploying hundreds of things once a day.

Make a change to a thing, which might take a few minutes or a few hours, get it reviewed and merged and it'll be in production a few minutes later.

Once you get past 500 engineers, even just completing a single task a week means 100 things to deploy every day: either you batch them together somehow or you work on the tooling to just get them to production without any fuss.