That sums it up very well for how I feel about both practices.
With large teams, especially if distributed or partially outsourced, code reviews can ensure code quality and are quite essential. It will allow you to share some knowledge and instill best practices. It will be a reminder for people that their code will be viewed by others so don’t take shortcuts.
However code review can also be a total bottleneck if over-bureaucratic. It will add an overhead for all work. If there are some high and mighty gate keepers that will stop you from pushing your code frequently then you have a complete velocity block. If your code is shit then fair enough, but if it is merely nit picking or just disagreements between styles then it is very costly. If however if any compulsory reviewer is not in your office, country, time zone or just very busy then that adds a large delay in the feedback loop.
Another issue with code reviews is that quite a few reviews are of low quality due to lack of context. They do not necessarily know all the discussions, history of why a piece of code works this way, project code style, etc. Especially if they are of the tainted ivory tower architect affliction.
In smaller, agile and especially collocated teams code reviews will flag issue unnecessarily late in the process. Just pair from the start instead to ensure no short cuts or dodgy code slips through, and automatically spread the knowledge. If you do not trust two of your developers combined then you do have a serious problem.
You can though in addition have small and short swarming/tripling/quadrupling sessions in front of 1 computer to look at especially important issues when they are worked on, not afterwards.
If you do neither code reviews nor pairing then you are in trouble.
Expanded from my own Hacker News comment https://news.ycombinator.com/item?id=6693064
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