Identifying Bottlenecks in Your Code Review Process

If your pull requests are taking days instead of hours to merge, you likely have a code review bottleneck. This guide breaks down the most common PR delays, shows you how to diagnose them with data, and provides actionable fixes used by high-performing engineering teams.

You open a PR on Monday morning. By Friday, it still hasn't been merged. What happened?

Code review bottlenecks are one of the most common causes of slow engineering velocity. They're also one of the most fixable—once you can see where the delays are actually happening.

The Anatomy of Code Review Delay

PR cycle time can be broken into stages. Each stage can become a bottleneck:

1. Pickup Time (PR Opened → First Review)

The PR sits in a queue waiting for someone to start reviewing. This is often the biggest bottleneck.

Common causes:

• No clear ownership of review responsibility
• Reviewers are overloaded
• Notifications are noisy and ignored
• PRs are too large to review quickly

2. Review Rounds (First Review → Final Approval)

Back-and-forth between author and reviewers. Multiple rounds of feedback and changes.

Common causes:

• Vague or inconsistent code standards
• Perfectionist reviewers (good is never good enough)
• Unclear requirements leading to design debates in review
• Author slow to respond to feedback

3. Merge Delay (Approved → Merged)

The PR is approved but not merged.

Common causes:

• Waiting for CI to pass (slow pipelines, flaky tests)
• Merge conflicts that need resolution
• Manual deployment gates or release train schedules
• Author forgot to click merge

How to Find Your Code Review Bottlenecks

Velocinator breaks down cycle time into these stages automatically. Here's how to diagnose your team's specific issues:

Check the Averages

Pull up your team's PR metrics. What's the median time for each stage?

Example:

• Pickup: 18 hours
• Review: 8 hours
• Merge: 2 hours
• Total: 28 hours

In this case, pickup is the clear bottleneck. The PR is approved in 8 hours once someone looks at it, but it takes 18 hours for that first look.

Look at the Distribution

Averages hide variation. Look at the histogram:

• 50% of PRs get reviewed within 4 hours
• 30% take 12-24 hours
• 20% take more than 48 hours

That long tail of 48+ hours is worth investigating. Are certain PRs systematically delayed? Why?

Slice by Repository

Some repos may have faster reviews than others. If the payments service has 3x longer pickup time than the frontend, there might be an ownership or expertise gap.

Slice by Author

Are certain developers' PRs consistently delayed? Maybe they're:

• Opening PRs too large to review easily
• Not tagging appropriate reviewers
• On a different timezone than most reviewers
• Junior devs whose code requires more scrutiny

Slice by Reviewer

Are certain reviewers creating bottlenecks? Maybe they:

• Are requested on too many PRs
• Have consistently slow response times
• Are too thorough (reviewing every PR like it's a PhD thesis)

Fixing Pickup Time

If PRs languish waiting for first review:

Implement Review Rotation

Assign a "reviewer on duty" each day. Their job is to triage incoming PRs and either review them or assign to the right person.

Set Team SLAs

Agree as a team: "All PRs get first review within 4 business hours." Make it visible who's waiting. Create gentle accountability.

Batch Review Time

Schedule dedicated review blocks (e.g., 9-10 AM and 2-3 PM). This protects both reviewer focus time and ensures regular review attention.

Reduce PR Size

Smaller PRs get reviewed faster. Set a soft limit (e.g., 400 lines) and break larger changes into incremental chunks.

Improve Notifications

Maybe reviewers aren't ignoring PRs—they're just not seeing them. Audit notification settings. Consider a dedicated Slack channel for PR requests.

Fixing Review Rounds

If PRs go through many rounds of feedback:

Establish Code Standards

Document and enforce style, patterns, and practices. Use linters and formatters to catch style issues automatically so reviews focus on substance.

Clarify Requirements Upfront

Design debates shouldn't happen in code review. Have architecture discussions before coding starts. Use RFCs or design docs for significant changes.

Coach Reviewers

Some reviewers need to learn the difference between "this must change" and "I would have done it differently." Not every suggestion needs to block merge.

Accelerate Author Response

If authors take days to respond to feedback, coach them on prioritizing review comments. A PR in review is inventory—you want to move it through the system.

Fixing Merge Delay

If approved PRs sit unmerged:

Speed Up CI

Invest in faster test suites, parallelization, and better caching. A 45-minute pipeline kills developer momentum.

Fix Flaky Tests

Tests that fail randomly teach developers to ignore failures. Fix or delete them.

Enable Auto-Merge

GitHub and GitLab support auto-merge after approval and passing CI. If there's no reason for a human to click the button, don't require it.

Address Merge Conflicts Quickly

Long-lived branches accumulate conflicts. Encourage frequent rebasing or merging from main.

The Continuous Improvement Loop for Code Review

Bottleneck analysis isn't a one-time exercise. Review it monthly:

1. Pull the metrics
2. Identify the biggest current bottleneck
3. Implement one improvement
4. Measure impact next month
5. Repeat

Over time, you'll systematically remove friction from your review process. A team that started with 5-day cycle time can often reach 1-2 days within a few months.

Start Diagnosing

Connect Velocinator to your GitHub, and review bottleneck analysis is available immediately. See exactly where your PRs are getting stuck.

Fast reviews aren't about pressuring people to work faster. They're about removing unnecessary delays so good work ships sooner.

For more on the human side of code reviews, read the psychology of code review. To understand how review delays connect to broader delivery metrics, see our PR cycle time guide.