Ask HN: When code review starts backing up on your team, what happens?

I've been a developer for about 20 years and this is the thing I've never seen handled well. On my teams it was usually me noticing a couple of days late and then pinging people.

Curious what other teams do in practice rather than in theory. A rotation? An SLA? A bot? Someone whose actual job it is to watch the queue? Or does it sort itself out on its own?