Code reviews are ubiquitous in software development, but many are ineffective. Some are rubber stamps that catch nothing. Others are adversarial battles that demoralize developers. Effective code reviews improve code quality, share knowledge, and build team culture.
Here’s how to do them well.
What Code Reviews Are For
Primary Goals
Catch bugs early: Finding issues before production is orders of magnitude cheaper than after.
Ensure maintainability: Code is read more than written. Reviews catch hard-to-maintain patterns.
Share knowledge: Reviews spread understanding of the codebase across the team.
Enforce consistency: Teams work better with consistent patterns and standards.
Secondary Benefits
Mentorship: Senior developers teach through review feedback.
Collective ownership: Multiple people understand each change.
Documentation: Review comments explain the “why” behind decisions.
As a Reviewer
Prepare Before Reviewing
Understand context:
- Read the issue/ticket
- Understand what problem is being solved
- Know what success looks like
Check the scope:
- Is this a bug fix, feature, or refactoring?
- What’s the expected impact?
- Are there related changes?
What to Look For
Correctness:
- Does it do what it’s supposed to?
- Are edge cases handled?
- Are error cases handled properly?
Design:
- Does it fit the existing architecture?
- Is the abstraction level appropriate?
- Are there better approaches?
Maintainability:
- Can someone else understand this code?
- Is it appropriately commented?
- Are names clear?
Performance:
- Any obvious performance issues?
- N+1 queries?
- Unnecessary allocations?
Security:
- Input validation?
- Authentication/authorization correct?
- Data exposure risks?
Testing:
- Are tests meaningful?
- Do they cover edge cases?
- Would they catch regressions?
How to Give Feedback
Be specific:
# Bad
"This code is confusing."
# Good
"This function does three things: parsing, validation, and storage.
Consider splitting into parseInput(), validateOrder(), and saveOrder()
so each function has a single responsibility."
Explain why:
# Bad
"Use a map here instead of a list."
# Good
"Looking up products by ID happens in the inner loop.
A map would give O(1) lookup instead of O(n), which matters
when processing large orders."
Suggest, don’t demand:
# Adversarial
"This is wrong. Fix it."
# Collaborative
"Have you considered using X here? It might handle
the edge case at line 45 more cleanly."
Distinguish severity:
[blocking] This SQL query is vulnerable to injection.
We need to use parameterized queries.
[suggestion] Consider extracting this logic into a helper function.
It would improve readability, but not blocking.
[nit] Typo in comment: "recieve" → "receive"
Ask questions:
"I don't understand why we need to check this condition twice.
Is there a case I'm missing, or could we simplify?"
Questions invite explanation rather than defensiveness.
Common Review Mistakes
Reviewing too much at once:
- Large reviews get superficial attention
- Break into smaller PRs or review in sections
Focusing only on style:
- Style issues are real but shouldn’t dominate
- Automate style with linters
- Focus review time on logic and design
Being too harsh:
- Code is personal; criticism feels personal
- Critique the code, not the coder
- Assume good intent
Being too nice:
- Rubber-stamp reviews catch nothing
- Honest feedback helps people grow
- Problems now prevent bigger problems later
Blocking on trivial issues:
- Not every suggestion needs implementation
- Perfect is the enemy of done
- Save major redesigns for major PRs
As an Author
Before Requesting Review
Self-review first:
- Read your own diff
- Catch obvious issues
- Ask: “Would I understand this in 6 months?”
Keep PRs small:
- ~200-400 lines is ideal
- Large PRs get worse reviews
- Split by logical unit of change
Write good descriptions:
## Summary
Adds rate limiting to the API to prevent abuse.
## Changes
- Implements token bucket algorithm in RateLimiter class
- Adds middleware to apply rate limiting
- Configurable limits per endpoint
## Testing
- Unit tests for rate limiter logic
- Integration tests for middleware
- Manual testing with load tool
## Related
- Fixes #123
- See RFC: [Rate Limiting Design]
Make the reviewer’s job easy:
- Clear commit history
- Logical organization
- Comments on tricky parts
Receiving Feedback
Don’t take it personally:
- Feedback is about code, not you
- Even harsh feedback has useful content
- Assume good intent
Engage with feedback:
- If you disagree, explain why
- Ask for clarification on unclear points
- Acknowledge valid points
Learn from patterns:
- If you get the same feedback repeatedly, address the root cause
- Track feedback to identify growth areas
Team Practices
Turnaround Time
Reviews should happen within hours, not days:
- Blocked developers are unproductive
- Context fades over time
- Long waits discourage small PRs
Set team norms: reviews within 4 working hours, for example.
Automate What You Can
Don’t waste human attention on automatable checks:
# CI checks
- Linting (style)
- Formatting (consistent code style)
- Type checking
- Test coverage
- Security scanning
- Build verification
Reserve human review for what humans do best: understanding intent and design.
Review Requests Distribution
Avoid single points of knowledge:
- Rotate reviewers
- Pair junior with senior reviewers
- Anyone can review (with appropriate expertise)
Review Checklist
## Review Checklist
- [ ] I understood the context and goals
- [ ] The code does what it's supposed to
- [ ] Edge cases are handled
- [ ] Error handling is appropriate
- [ ] Tests are meaningful
- [ ] No security concerns
- [ ] No performance concerns
- [ ] Code is maintainable
Handling Disagreements
When reviewer and author disagree:
- Discuss in the PR (or synchronously if complex)
- Focus on trade-offs, not preferences
- If deadlocked, involve a third party
- Accept that reasonable people can disagree
- Make a decision and move on
Measuring Review Effectiveness
Track metrics to improve:
- Time to first review: How quickly do reviews start?
- Review cycles: How many back-and-forths per PR?
- Bugs escaping review: What do we miss?
- Team satisfaction: Do people find reviews useful?
Key Takeaways
- Code reviews catch bugs, ensure maintainability, share knowledge, and enforce consistency
- Reviewers: understand context, look for bugs/design/maintainability, be specific, explain why
- Use severity markers (blocking, suggestion, nit) to clarify importance
- Ask questions rather than making demands
- Authors: self-review first, keep PRs small, write good descriptions
- Receive feedback gracefully; it’s about the code, not you
- Set team norms for review turnaround time
- Automate style and formatting checks; focus human review on logic and design
- Handle disagreements through discussion, not diktat
Good code reviews make both the code and the team better. Invest in doing them well.