I did not do any OKRs on an infrastructure team. Qualitative results were just as valued, and we had the quantitative knobs to dial when needed thanks to excellent internal tooling and service maturity.
I found it to be the ironic part of working at one of the most data-driven companies. We didn’t do OKRs in my org despite using data to drive decisions. I much prefer this to OKR hell.
It depends substantially based on which org you are in. But generally it is at the team level, so it would mostly be on the EM/TL/senior eng on the team.