Knowing how to do code review is a crucial skillset that modern engineers need to safeguard code quality and team velocity. By mastering a research-backed review workflow, you can prevent an otherwise healthy codebase from silently eroding over time while still shipping features fast.
In this comprehensive walkthrough on how to do code review effectively, you'll learn why collaboration, systematic inspection, and crystal-clear feedback make the biggest difference. Much of what you're about to read is informed by Google's engineering practices and industry best practices, though not all recommendations are directly grounded in peer-reviewed studies.
Effective code review hinges on three core competencies:
- A collaborative mindset that treats reviews as continuous-improvement opportunities, not gatekeeping rituals.
- A methodical checklist that inspects every change for correctness, security, performance, maintainability, and test coverage.
- Labeled feedback conventions that cleanly separate blocking issues from friendly suggestions.
TL;DR
Review quality depends more on reviewer mindset and a repeatable process than on raw technical prowess. Industry experience consistently shows that smaller pull requests receive more thorough reviews, two reviewers typically detect the optimal number of defects before diminishing returns set in, and maintaining a measured review pace catches significantly more bugs than rushing through large changesets. Batching reviews into focused time blocks helps developers avoid the productivity loss caused by constant context switching.
Why Learning How to Do Code Review Matters
Countless engineering teams still lack a structured code review framework, leading to inconsistent feedback, sluggish approvals, and either missed defects or needless blocking over trivia. Engineering organizations like Google, Microsoft, and Meta have documented that the most successful reviewers share three traits: a mindset devoted to continuous improvement, a repeatable inspection checklist, and constructive communication anchored by clear labels.
The real purpose of any code review is to make sure that the overall code health of the codebase is improving over time. In other words, code review is a lever for continuous improvement, not merely a quality gate.
Industry experience consistently shows that catching defects during code review is significantly cheaper than fixing them in production. Unfortunately, poorly structured reviews often miss the bugs that matter while sparking friction over subjective preferences.
This practical guide unifies best practices from Google, Microsoft, Meta, and widely-adopted industry standards into one actionable blueprint. By the end, you'll know the exact mindset shifts, evaluation criteria, comment patterns, and time-management tactics that separate high-impact reviewers from rubber-stampers.
Want to upgrade your team's review workflow? Augment Code's Context Engine uncovers hidden dependencies across entire codebases, helping reviewers catch architectural issues that file-isolated analysis misses. Explore Context Engine capabilities →
Why Code Review Mindset Drives Quality
Your approach to code review matters more than your technical expertise. The following principles shape how effective reviewers think about their role and interact with code authors.
Continuous Improvement Beats Perfectionism
Google's engineering practices remind reviewers that "perfect code" is a myth; the real goal is better code. Meta engineers have similarly found that emphasizing improvement over perfection shortens review cycles and boosts developer satisfaction without sacrificing quality.
Psychological Safety Starts With the Reviewer
Google's Project Aristotle found that psychological safety is the top predictor of team success, a principle that applies directly to code reviews. Reviewers who frame feedback as joint problem-solving, admit their own blind spots, and remain aware of power dynamics foster safer, more productive discussions.
Beware Cognitive Biases
| Bias | What Happens | How to Counter |
|---|---|---|
| Confirmation | Reviewer hunts only for problems they expect | Read tests first, then implementation |
| Authority | Junior authors get extra scrutiny | Apply the same documented standards to everyone |
| Anchoring | First impression colors the whole review | Make multiple passes, each with a different focus |
What to Check During a Code Review
Systematic inspection across five dimensions yields the highest defect-detection rates. Teams that follow enterprise coding standards catch more defects through consistent evaluation criteria.
1. Correctness & Logic
Verify that the change implements business rules accurately, handles edge cases (nulls, maxima, minima, empties), uses correct control flow and algorithms, and maintains data integrity throughout the system.
Augment Code's Context Engine accelerates this step by surfacing cross-service impacts automatically.
2. Security
Follow the OWASP Code Review Guide by scanning for injection flaws (SQL, command, LDAP), authentication and session weaknesses, XSS vectors, broken access control or privilege escalation, sensitive-data leaks, CSRF gaps, and dependency vulnerabilities.
3. Performance
Look for time and space complexity issues, database query problems (indexes, N+1, connection pooling), and resource management concerns (memory, CPU, I/O, caching).
4. Readability & Maintainability
Confirm clear naming, single-purpose functions, logical file organization, comments that explain "why," and consistent formatting. Teams that invest in code documentation practices reduce review friction significantly.
5. Tests
Ensure adequate coverage of new paths and edge cases, precise assertions (not just "no error" checks), and independent, deterministic tests of the right type (unit, integration, end-to-end). Following unit testing best practices helps reviewers evaluate test quality effectively.
How to Write Constructive Review Comments
The way you phrase feedback determines whether authors feel supported or attacked. These conventions help reviewers communicate clearly while maintaining positive working relationships.
Use Conventional Comments Labels
Labels like praise:, nitpick:, suggestion:, issue:, question:, thought:, and chore:, plus (blocking) or (non-blocking) decorations, remove any ambiguity about urgency. The Conventional Comments specification provides a standardized approach.
Example:
Be Specific and Actionable
Good: "Using map() would shorten the loop and clarify intent." Bad: "Too complex."
Ask Questions, Don't Dictate
Collaborative: "Would async/await make the error flow clearer?" Directive: "Use async/await."
Flag Blocking vs. Non-Blocking Issues
Blocking issues include security holes, functionality bugs, clear performance regressions, or violations of documented standards. Non-blocking issues include stylistic preferences or nice-to-have refactors.
Augment Code's Context Engine helps teams surface hidden dependencies and architectural impacts during review, reducing missed defects across large codebases. Explore architectural analysis capabilities →
Managing Review Time Like a Pro
How you structure your review time affects both your productivity and the quality of your feedback. These time-management strategies help reviewers maintain focus without letting PRs pile up.
Batch Reviews Into 60-90-Minute Sessions
Context switching significantly reduces productivity. Reserve two or three review blocks per day, keep each to 60-90 minutes, and use the morning for deep feature work. Teams struggling with context switching can leverage AI tools to maintain focus.
Keep PRs Under 400 Lines
Smaller pull requests receive more thorough reviews and faster turnaround. Industry analysis from SmartBear suggests that review effectiveness declines sharply for larger changesets:
| PR Size | Typical Review Time | Quality |
|---|---|---|
| 1–200 LOC | ≈ 45 min | Best |
| 201–400 LOC | 1–2 h | Good |
| 400+ LOC | 2 h+ | Declining |
When a PR exceeds 400 lines, request splits unless there's a compelling reason.
Balance Reviews With Feature Work
Aim for roughly 70% feature development and 30% reviews/collaboration to maintain momentum without sacrificing code health.
Code Review Anti-Patterns to Avoid
Even experienced reviewers fall into counterproductive habits. Watch out for these common mistakes that slow down teams and frustrate authors:
- Nitpicking over style instead of leaving formatting to automated linters.
- Rubber-stamping PRs instead of conducting real scrutiny.
- Perfectionist blocking instead of accepting working improvements.
- Applying inconsistent standards instead of treating all authors equally.
- Introducing scope creep instead of focusing on the PR's stated purpose.
What to Do Next
Effective code review follows a systematic process: adopt a continuous-improvement mindset, inspect every change across correctness, security, performance, readability, and tests, and use labeled comments to distinguish blocking issues from suggestions. Reviewers who enforce a 400-line PR limit and batch reviews into focused sessions catch more defects while maintaining team velocity.
Augment Code's Context Engine surfaces cross-service dependencies across 400,000+ files, helping reviewers catch architectural issues that file-isolated analysis misses. Explore Context Engine capabilities →
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Written by
Molisha Shah
GTM and Customer Champion