Advantages of code review

Advantages of pre-deploy code review, over post-deploy audit:

• Authors have a strong incentive to craft small, well-formed changes that will be readily understood, to explain them adequately, and to provide appropriate test plans, test coverage and context.
• Reviewers have a real opportunity to make significant suggestions about architecture or approach in review. These suggestions are less attractive to adopt from audit, and may be much more difficult to adopt if significant time has passed between push and audit.
• Authors have a strong incentive to fix problems and respond to feedback received during review, because it blocks them. Authors have a much weaker incentive to address problems raised during audit.
• Authors can ask reviewers to apply and verify fixes before they are pushed.
• Authors can easily pursue feedback early, and get course corrections on approach or direction.
• Reviewers are better prepared to support a given change once it is in production, having already had a chance to become familiar with and reason through the code.
• Reviewers are able to catch problems which automated tests may have difficulty detecting. For example, human reviewers are able to reason about performance problems that tests can easily miss because they run on small datasets and stub out service calls.
• Communicating about changes before they happen generally leads to better preparation for their effects.