Code Review Time: Optimising Your Team's Review Process

Why Code Review Time Matters

Code review time is often the single largest contributor to lead time for changes. A developer may spend a day writing code, but the resulting pull request can sit in a review queue for days. This waiting time is pure waste from a lean perspective: it delays delivery, creates context-switching overhead when reviewers finally engage, and demoralises developers who see their work languishing.

Long review times also compound. When developers know reviews take days, they batch more changes into larger pull requests. Larger pull requests take even longer to review, creating a vicious cycle. Breaking this cycle by reducing review time leads to smaller, more focused pull requests that are easier to review, creating a virtuous cycle instead.

Beyond pipeline efficiency, code review is a critical quality and knowledge-sharing practice. Effective reviews catch bugs, improve code quality, spread knowledge across the team, and mentor junior developers. But these benefits only materialise when reviews are timely and thorough, not when they are rushed or delayed.

Measuring Code Review Time

Code review time can be broken into several components: time to first review (from PR creation to the first substantive comment), review turnaround time (time between review rounds), and total review duration (from PR creation to final approval). Each component reveals different bottlenecks.

Most source control platforms (GitHub, GitLab, Bitbucket) provide data on pull request timelines. Dedicated engineering analytics tools like LinearB, Jellyfish, or Pluralsight Flow can aggregate this data and provide team-level dashboards. Track median values and 90th percentiles for each component.

• Track time to first review as the primary indicator of reviewer responsiveness
• Measure total PR duration from creation to merge for end-to-end review time
• Monitor the number of review cycles per PR as an indicator of review effectiveness
• Segment by PR size to understand how size affects review time
• Track reviewer workload distribution to ensure reviews are shared fairly

Code Review Time Benchmarks

High-performing teams aim for first review within 4 hours and total PR duration under 24 hours. Google's engineering practices recommend that code reviews should be completed within one business day. Many elite teams achieve even faster turnaround, particularly when they keep pull requests small and focused.

If your team's median time to first review exceeds 24 hours, you have a significant bottleneck to address. PRs waiting more than two days for initial review are strongly correlated with developer frustration and reduced delivery speed. This is often the first metric engineering managers should tackle when improving lead time.

Review time tends to increase with PR size. Pull requests under 200 lines of changed code are typically reviewed 2-3 times faster than those over 500 lines. This relationship underscores the importance of keeping PRs small as a strategy for improving review time.

Strategies to Reduce Code Review Time

Establish clear review SLAs with your team. A common and effective SLA is: first review within 4 hours during working hours. Make this a team norm, not a management mandate. Discuss the rationale (faster delivery, better flow) and get team buy-in. Most developers understand the frustration of waiting for reviews and willingly support SLAs.

Enforce PR size limits. Many teams set a soft limit of 200-400 lines of changed code per PR. Automated tools can flag oversized PRs and suggest splitting them. When PRs are small, reviews are faster, more thorough, and less mentally taxing for reviewers.

• Set and enforce review SLAs (e.g., first review within 4 hours)
• Limit PR size to 200-400 lines of changed code
• Rotate review responsibilities to prevent bottlenecks on specific reviewers
• Use automated linting and formatting to eliminate nitpick-style review comments
• Provide clear PR descriptions and context to speed up reviewer comprehension

Balancing Review Speed with Review Quality

Faster reviews should not mean superficial reviews. The goal is to reduce wait time, not review thoroughness. Achieving both requires structural changes: smaller PRs that are genuinely faster to review thoroughly, clear review checklists that focus attention on high-impact concerns, and automated tools that handle mechanical checks.

Consider implementing tiered review approaches for different types of changes. Critical path code and security-sensitive changes may warrant more thorough review, whilst configuration changes and documentation updates may need lighter review. Define review expectations by change type to allocate review effort efficiently.

Pair programming and mob programming can reduce or eliminate the need for asynchronous code review. When two developers collaborate on code in real time, the review happens during development. This approach can dramatically reduce lead time whilst maintaining or improving code quality.

Key Takeaways

• Code review time is often the largest contributor to lead time and a high-leverage improvement area
• Aim for first review within 4 hours and total PR duration under 24 hours
• Small PRs (under 200-400 lines) are reviewed faster and more thoroughly
• Review SLAs, size limits, and automated formatting checks are the most effective interventions
• Pair programming can eliminate asynchronous review delays entirely