It depends on what is required from the reviewers.
If you have a pair with 1 person with good knowdledge of the code digging deep into what the PR/MR does, and another dev just checking for anything surprising, or even just validating that what you're doing makes sense at the surface, that will probably cover most bases.
If you have a pair with 1 person with good knowdledge of the code digging deep into what the PR/MR does, and another dev just checking for anything surprising, or even just validating that what you're doing makes sense at the surface, that will probably cover most bases.