It's interesting to hear this - can you expand?
Is the frustration level a constant problem if reviews can take ... X longer than thought?
I'm an SRE, which means most of the code I write isn't directly user-facing, and thus isn't normally subject to hard external launch deadlines. That means I'm rarely rushing to push my changes through on a tight schedule. If there's a production emergency and I need to make an urgent change to avoid or mitigate an outage, there are escape hatches at our disposal to temporarily circumvent the code review system when no one is immediately available to do a review, but the need for that is pretty infrequent.
I rarely find it frustrating. On the contrary, I really appreciate Google's emphasis on code quality, even though it does come at the cost of some agility. I used to work at a company where the implementation of code reviews was generally resisted, and though we did get new code out the door faster, we ended up with some real maintenance nightmares as a result.
I've seen lots of self-+2s under the following circumstances:
1. You are the only engineer on your team, or all other engineers on your team are out for an extended period of time.
2. All other engineers have very different skillsets, and are not capable of doing effective review. Think Rails engineer attempting to review a touchpad firmware fix.
3. You have a hard deadline (e.g. product demo or factory build) and you're desperately trying to get as much working as you can. You may even be in a location where coordination is difficult and Internet access is poor.
For SWEs working on, say, web services, you probably have at least a medium-sized team (4+ engineers) and a week's slip is no big deal. But not all software is like that at Google.