Why would reviewing have to be done by a specific individual? If reviewing is the blocker, you need to raise the priority and allocate more resources to it.
For me code reviews are falling in two categories:
1. Just pass it by a second pair of eyes to make sure I'm mot doing anything really dumb or nefarious. Here I don't care who reviews it, and in my team the person currently on-call is usually the choice.
2. I'm working on something complex or that I'm not yet familiar with. In that case, I want a specific person, who I know is familiar with the technology or the project.
I work for FAANG and making changes to code owned by a team in the US is very common. However I'm from Europe and nobody else around me can review that code.
