What Senior Engineers Actually Do During Code Reviews (It's Not Just Finding Bugs)
The best code review comment I have learned to leave is not: This has a bug. It is: Should this code exist here at all? A change can be locally correct and systemically wrong. The code is clean. The tests pass. The author's reasoning makes sense. But the change puts a new responsibility in the wrong service, duplicates a rule owned elsewhere, or establishes a pattern the team will spend years…
Senior engineers focus their code review efforts beyond merely identifying bugs. In a study conducted by Microsoft, researchers observed developers and classified 570 review comments. They found that while 44% of developers considered bug finding the top motivation for reviews, only 14% of the analyzed comments were related to defects. The majority, 29%, were code improvements such as removing unnecessary code or enhancing readability.
The researchers concluded that code reviews primarily serve to maintain the integrity of codebases and establish norms around readability and consistency. By shifting the focus from merely checking if the implementation is correct to questioning if it belongs, senior reviewers create more leverage in their reviews.
When reviewing code, senior engineers look for four key signals that warrant a pause. First, they consider the phrase "While we're here" – if a small change leads to nearby cleanups, validations, or optimizations, they question whether the change would still be made here without those additional conveniences. Second, they assess any new cross-boundary dependencies – if a service starts calling another service from a previously unused path or if a domain package imports an infrastructure client, they question which boundary has changed and who owns the new failure mode.
Third, they examine if a rule that already exists elsewhere is being reinvented in the current change. If the diff validates, calculates, normalizes, or authorizes something that another component already handles, the reviewer pauses to consider whether the responsibility should be centralized. Lastly, they evaluate if the change introduces a new pattern that the team may need to spend years undoing.
By asking these questions, senior engineers ensure that changes not only work correctly but also belong in their designated place within the system.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
