> At 37signals we work in teams of two, one designer, one programmer; and we ship projects in 6 weeks or less.

I'm curious how PR reviews work in this case. Does someone outside of the team review them?

There's no rule that says code needs to reviewed by someone else in a PR.

On small teams I've found it pragmatic for each specialist just to merge his/her own PRs and to schedule occasional code reviews instead.

(Unaffiliated with 37signals)