Code Review Best Practices: Complete Guide to Pull Request Reviews (GitHub & Azure DevOps)

May 8, 2026

Discover code review best practices, effective code review process, and pull request review techniques. Master GitHub pull request reviews and Azure DevOps code review workflows.

GitHub

Azure DevOps

~12 min read

Everything your team needs to run an effective code review process — from opening a PR to approving the final merge. Practical, opinionated, and tool-specific.

What Is Code Review in Software Engineering?

Definition

Code review in software engineering is a systematic examination of source code by one or more developers who did not write it. The goal is to identify defects, share knowledge, and ensure the codebase adheres to the team’s agreed-upon standards — all before the code reaches production.

At its most common, this happens through a pull request (also called a merge request). One developer opens a PR with their changes; others examine, comment, and either approve or request revisions. It’s the last human checkpoint before code enters the main branch.

Code Review by the Numbers

Teams that practice structured code review ship 60% fewer bugs to production, reduce onboarding time for new engineers by up to 40%, and report significantly higher code quality scores compared to teams that skip review entirely.

Why It Matters

There are three core reasons every engineering team should treat code review as a non-negotiable part of the development workflow:

Quality gate. A reviewer catches edge cases, logic errors, and security issues that automated tests miss. Two pairs of eyes consistently outperform one.
Knowledge sharing. When developers read each other’s code, they stay up to speed with changes across the codebase. Silos disappear. Bus-factor risk drops.
Bug prevention. Catching a bug in review costs a fraction of what it costs to fix in production — in time, reputation, and sometimes revenue.

Terminology note

GitHub calls them Pull Requests (PRs). GitLab and Azure DevOps call them Merge Requests (MRs). The process and best practices are identical — only the label differs.

Code Review Process (Step-by-Step)

A repeatable, team-wide code review process removes ambiguity and keeps velocity high. Here is the five-stage flow that scales from startup to enterprise:

Create the Pull Request

The author pushes a feature branch and opens a PR against main (or the relevant base branch). A meaningful title and a PR template description come first — reviewers should never have to guess what they’re looking at.

Assign Reviewers

Assign at minimum one domain expert and one general reviewer. For security-sensitive changes, involve a dedicated security reviewer. Keep the count between 1–3 — too many reviewers create diffusion of responsibility.

Work Through the Review Checklist

Reviewers examine the code against a shared checklist: correctness, security, performance, readability, test coverage. Inline comments are left for specific lines; general feedback goes in the summary.

Author Responds & Iterates

The author addresses feedback — either by making changes or by explaining the intent when the reviewer had a misunderstanding. Conversations are resolved once both parties are satisfied. The PR is updated and reviewers are notified to re-review.

Approval & Merge

Once all required reviewers approve and CI passes, the PR is merged — typically by the author or a designated team lead. The branch is deleted and the ticket is closed.

Day in the life: a 3-person backend team

Ana opens a PR for a new payment endpoint. She sets Bob (domain expert) and Clara (security reviewer) as reviewers. Bob finds a missing null check on line 47; Clara flags that the API key is logged in plaintext. Ana pushes a fix within an hour. Both reviewers resolve their threads and approve. CI passes. Ana merges to main. Total review time: 45 minutes. Production incidents prevented: at least 2.

Code Review Best Practices

These code review good practices apply regardless of the tool you use — GitHub, Azure DevOps, GitLab, or anything else. Adopt these as team norms, not individual habits.

Keep PRs Small

Large PRs are the single biggest destroyer of review quality. When a reviewer faces 1,200 lines of diff, they skim. When they face 150 lines, they read carefully. Aim for PRs that do one thing and do it completely.

Anti-pattern

One PR refactors the data layer, adds a new feature, and updates logging — 2,400 lines changed across 47 files.

Best practice

Three separate PRs, each scoped to a single concern. Reviewers can approve each in under 20 minutes.

Write a Clear PR Description

Every PR description should answer three questions without the reviewer having to ask:

What changed? — A plain-language summary of the diff.
Why? — Link to the ticket, spec, or the business reason.
How to test? — Steps to reproduce the scenario, or what automated tests cover it.

PR Template

## What changed?
Replaced synchronous DB calls in `OrderService` with async/await
to reduce P95 latency on the checkout endpoint.

## Why?
Resolves JIRA-4821 — checkout was blocking the event loop under load.

## How to test?
1. Run `npm test -- --testPathPattern=order`
2. Manually: POST /api/checkout with payload in `docs/test-payloads.json`
3. Check that response time < 200ms in staging

## Screenshots / logs
Before: avg 640ms · After: avg 138ms (load test attached)

## What changed?
Replaced synchronous DB calls in `OrderService` with async/await
to reduce P95 latency on the checkout endpoint.

## Why?
Resolves JIRA-4821 — checkout was blocking the event loop under load.

## How to test?
1. Run `npm test -- --testPathPattern=order`
2. Manually: POST /api/checkout with payload in `docs/test-payloads.json`
3. Check that response time < 200ms in staging

## Screenshots / logs
Before: avg 640ms · After: avg 138ms (load test attached)

Focus on Logic, Not Style

Style debates — trailing commas, brace position, quote style — belong in a linter config, not in code review comments. If your team spends even 10% of review time on formatting, you’re wasting engineering hours. Automate style; humanize logic.

Best Practice

Configure ESLint, Prettier, Black, Checkstyle, or the linter appropriate to your stack to run as a CI step. A PR with failing lint should never reach human reviewers.

Use Automation (Linters, CI, Static Analysis)

Automation handles the mechanical. Humans handle the meaningful. Your review pipeline should include:

Linters & formatters — catch style and syntax issues.
Unit & integration tests — must pass before review begins.
Static analysis — SonarQube, Semgrep, or CodeClimate for security and complexity issues.
Dependency scanning — Dependabot, Snyk, or similar.

Be Constructive, Not Critical

The goal of a review comment is to improve the code, not to demonstrate your knowledge or authority. Frame feedback as suggestions, ask questions instead of making demands, and always explain why a change matters.

Unhelpful comment

“This is wrong. Use a HashMap.”

Constructive comment

“Would a HashMap work here? The linear scan in the loop is O(n²) — this might become a bottleneck if the list grows beyond a few hundred items.”

Pull Request Review Best Practices

Being a great reviewer is a skill. Here is how to approach a pull request review efficiently and thoroughly.

How to Review Efficiently

Read the description first. Understand the intent before reading a single line of code.
Start with the high-level. Look at the file list. Is the scope right? Any unexpected changes?
Then go deep. Focus on the core logic files. Save tests and config for last.
Timebox it. 60 minutes per session max. Attention degrades sharply after that.
Review in one pass. Don’t dip in and out of the same PR over days. Block time and finish.

What to Look For

Reviewer focus areas

✓ Correctness: Does the code do what it claims? Are edge cases handled?
✓ Readability: Can a new team member understand this in 5 minutes?
✓ Performance: Any N+1 queries, blocking calls, or unnecessary allocations?
✓ Security: Is input validated? Are secrets handled correctly? SQL injection risk?
✓ Test coverage: Are new branches and error paths tested?
✓ API contracts: Are breaking changes documented and versioned?
✓ Dependencies: Are new libraries justified? Are they maintained and licensed correctly?

Common Reviewer Mistakes

Watch out for these

Nitpick overload — drowning the author in minor comments obscures the important ones. Approval without reading — rubber-stamping creates false confidence. Late-stage architecture feedback — if the approach is fundamentally wrong, say so early via a design doc, not after 500 lines are written.

The “LGTM” Problem

A team with a culture of fast approvals merged a PR that introduced an unindexed query on a table that would grow to 50M rows. The reviewer left one comment about a variable name and approved. Three weeks later, a full-table scan took down the API. A thorough pull request review would have caught this with a single question: “How does this query perform as orders scales?”

How to Review Pull Requests in GitHub

GitHub review pull request functionality is built into the PR interface. Here’s the complete workflow for both authors and reviewers.

Requesting a Review

When you open a PR, use the Reviewers sidebar on the right to add reviewers by username or team name. GitHub will notify them immediately. You can also use CODEOWNERS to auto-assign reviewers for specific directories:

github/CODEOWNERS

# Global owners
*                   @org/core-team

# Backend services
/src/api/           @org/backend-team

# Infrastructure changes always reviewed by DevOps
/infra/             @org/devops @alice
/docker/            @org/devops

# Payments: two required reviewers
/src/payments/      @bob @carol

# Global owners
*                   @org/core-team

# Backend services
/src/api/           @org/backend-team

# Infrastructure changes always reviewed by DevOps
/infra/             @org/devops @alice
/docker/            @org/devops

# Payments: two required reviewers
/src/payments/      @bob @carol

GitHub tip

Enable Branch Protection Rules (Settings → Branches) to require at least one review approval before merging. This enforces the github request review step for every PR automatically.

Leaving Comments

GitHub offers three types of feedback during a github review pull request:

Line comments — Click the + on any diff line to leave specific inline feedback. You can comment on a single line or drag to select a range.
Suggested changes — Use the suggest block to propose an exact code replacement the author can accept with one click.
General review summary — Submitted when you finish the review, visible at the top of the PR timeline.

Suggested change syntax

Consider using optional chaining here to avoid the null check:

```suggestion
const userName = user?.profile?.name ?? 'Anonymous';
```

This removes the explicit null guard and is safer if
`profile` is also nullable.


Consider using optional chaining here to avoid the null check:

```suggestion
const userName = user?.profile?.name ?? 'Anonymous';
```

This removes the explicit null guard and is safer if
`profile` is also nullable.

Approving or Requesting Changes

When you click Finish your review, GitHub asks you to choose one of three states:

Comment — Feedback without a formal vote. Use for questions or FYI notes.
Approve — You’re satisfied. The PR is ready to merge (pending other required approvals).
Request changes — The PR must not be merged until specific issues are addressed. The author will be notified and the PR will be marked as blocked.

The full GitHub PR Review loop

Open PR → assign reviewers via CODEOWNERS or manually → reviewer leaves inline comments and a suggested change or two → submits “Request changes” → author addresses feedback and re-requests review → reviewer approves → branch protection confirms CI passes → merge.

How to Do Code Review in Azure DevOps

Azure DevOps code review happens through Pull Requests inside Azure Repos. The workflow is similar to GitHub but with some enterprise-grade policy controls built in.

Pull Request Workflow in Azure DevOps

Push your branch and navigate to Repos → Pull Requests → New Pull Request.
Set the source and target branch, add a title and description.
Add reviewers — individually or from a team. Mark reviewers as Required or Optional.
Link work items (user stories, bugs) to give context to the review.
Submit the PR — reviewers are notified automatically.

Branch Policies

Azure DevOps lets you enforce merge requirements through Branch Policies (Project Settings → Repos → Policies). Recommended settings for a team enforcing strong code review good practices:

YAML – Recommended branch policy config

# Azure DevOps Branch Policy (conceptual representation)

branch: main

policies:
  minimum_approvers: 2
  require_linked_work_items: true
  reset_votes_on_push: true       # reviewers must re-approve after new commits
  allow_requester_to_approve: false

build_validation:
  - pipeline: ci-build
    trigger_type: automatic
    required: true

comment_requirements: Required       # all threads must be resolved before merge

# Azure DevOps Branch Policy (conceptual representation)

branch: main

policies:
  minimum_approvers: 2
  require_linked_work_items: true
  reset_votes_on_push: true       # reviewers must re-approve after new commits
  allow_requester_to_approve: false

build_validation:
  - pipeline: ci-build
    trigger_type: automatic
    required: true

comment_requirements: Required       # all threads must be resolved before merge

Azure DevOps tip

Enable “Reset all approval votes when new changes are pushed”. This prevents a common failure mode where reviewers approve early and a last-minute commit slips through without re-review.

Merge Requirements & Completion

Azure DevOps supports four merge strategies. Choose based on your team’s preference for history clarity:

Merge commit — Preserves full history. Best for audit trails.
Squash merge — Collapses the branch into one commit. Cleanest main history.
Rebase and fast-forward — Linear history without merge commits.
Semi-linear merge — Rebase first, then merge commit. A middle ground.

How a 40-person team uses Azure DevOps policies

A fintech team requires 2 approvals on main: one from the owning squad, one from a security reviewer for any change touching /src/payments/. Build validation runs a 12-minute CI pipeline. Comment resolution is mandatory. Auto-complete is enabled — once all conditions are met, the PR merges without the author having to return. This setup catches issues without creating merge bottlenecks.

Code Review Checklist (Quick Reference)

Use this checklist as a shared team reference. Pin it to your wiki, drop it into your PR template, or use it as a reviewer’s starting point before writing the first comment.

Security

✓ All user inputs are validated and sanitized
✓ No secrets, API keys, or credentials in code or logs
✓ Authentication and authorization are checked at the right layer
✓ SQL queries use parameterized statements (no string concatenation)
✓ Dependency versions are pinned and not known-vulnerable
✓ Error messages don’t leak internal stack traces to clients

Performance

✓ No N+1 database queries inside loops
✓ Expensive operations are not duplicated unnecessarily
✓ Large data sets are paginated, not loaded into memory at once
✓ Caching is used where appropriate (and invalidated correctly)
✓ Algorithmic complexity is reasonable for expected data size

Readability

✓ Variable and function names clearly describe intent
✓ Functions are short and do one thing
✓ Complex logic has explanatory comments (not noise comments)
✓ No dead code, commented-out blocks, or debug statements
✓ Code follows team conventions consistently

Tests

✓ New logic is covered by unit tests
✓ Error paths and edge cases have dedicated test cases
✓ Tests have descriptive names that explain the scenario
✓ No tests are skipped or commented out without explanation
✓ Integration tests cover the critical path end-to-end

Ship this to your team

Add this checklist to your .github/pull_request_template.md (GitHub) or the PR description template in Azure DevOps project settings. When it’s visible in every PR, reviewers use it automatically — no reminders needed.

SUMMARY

A great code review process is small PRs with clear descriptions, automated style checks, human reviewers focused on logic and security, and a culture where feedback is specific, kind, and always explains the why.

Want to improve your Git workflow even further? Check out my guides on Git Branch Naming Conventions and Best Branching Git Workflow to Follow for cleaner, more scalable development practices.