Scaling Code Reviews: A Two-Step Process for Large Engineering Teams

Code reviews are a cornerstone of software development, ensuring code quality, consistency, and maintainability. But as engineering teams grow, managing code reviews can become challenging. A two-step code review process balances quality control with scalability, fostering collaboration across all levels of the team.

In this article, we’ll explore the benefits of a two-step code review process, provide an example workflow, and show how it improves code quality while reducing bottlenecks.

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Why Adopt a Two-Step Code Review Process?

The two-step process incorporates both peer reviews and lead or senior developer reviews, creating a layered approach that combines diverse perspectives and high-level oversight. Here’s why it works:

1. Improved Code Quality
   
   Peer reviews encourage developers to collaborate and catch issues early. Senior reviews add a layer of architectural and consistency checks, ensuring the code aligns with broader goals.

2. Shared Ownership
   
   When peers review code, they take collective responsibility for its success, fostering a sense of teamwork and shared accountability.

3. Mentorship and Growth
   
   Junior developers learn by reviewing code and receiving constructive feedback. Senior developers reinforce best practices and align the team on coding standards.

4. Scalability and Efficiency
   
   With multiple people sharing the review workload, bottlenecks are minimized. Breaking reviews into two steps allows peers to handle functional testing while seniors focus on consistency and maintainability.

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The Two-Step Process in Action

Here’s how the two-step review process can be implemented effectively:

Step 1: Peer Review

The first review is conducted by a peer developer—or two, for complex tasks.

Responsibilities of the Peer Reviewer:

• Pull the code, run it locally, and confirm it meets the acceptance criteria.
• Test edge cases and error-handling scenarios.
• Ensure the solution works as intended, just as thoroughly as the original developer would.

Example Scenario:

A developer, Alex, implements a feature to allow users to reset their passwords via email. After completing the code, Alex tags two peers, Taylor and Jordan, as reviewers in the task management tool (e.g., Jira).

Taylor:

• Pulls the branch and confirms that entering a valid email triggers the expected behavior.
• Tests edge cases, like invalid emails or rate-limiting scenarios.
• Leaves comments suggesting better error handling for a rare edge case.

Jordan:

• Checks that the code follows the project’s coding guidelines.
• Runs unit tests to ensure all cases are covered and suggests improving test coverage for one function.

Together, Taylor and Jordan give the feature a thorough review, improving its robustness.

Step 2: Lead or Senior Review

After peer review, the code is passed to a lead or senior developer for final approval.

Responsibilities of the Senior Reviewer:

• Focus on code consistency, patterns, and maintainability.
• Ensure alignment with architectural principles and team standards.
• Provide constructive feedback to ensure long-term codebase health.

Example Scenario (Continued):

Once Taylor and Jordan approve the changes, the ticket moves to Riley, the team lead. Riley:

• Examines how the password reset logic interacts with other parts of the system, ensuring no unintended side effects.
• Reviews the implementation for adherence to DRY (Don’t Repeat Yourself) principles and suggests refactoring duplicated logic into a reusable utility function.
• Provides a brief explanation of why the change aligns with broader architectural goals, using it as a teaching moment for the team.

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Key Benefits of the Two-Step Process

1. Catch Issues Early and Often
   
   Peer reviews focus on functionality and edge cases, ensuring that code is feature-complete and error-free before it progresses. Senior reviews add a final layer of polish, catching higher-level issues like redundancy or misaligned patterns.

2. Foster Collaboration
   
   By engaging multiple people in the process, you create opportunities for cross-training, knowledge sharing, and mentorship.

3. Encourage Standardization
   
   Senior developers can act as gatekeepers of coding standards and best practices, ensuring consistency across the team while helping juniors grow.

4. Reduce Bottlenecks
   
   Peer reviews distribute the workload, and senior reviews ensure that no single person is a bottleneck for progress.

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Tips for Implementation

• Use Clear Tools and Labels: In your task management tool (e.g., Jira or Trello), create a dedicated “Reviewer” label and specify whether the ticket is in the peer review or senior review stage.
• Define SLAs for Reviews: Set expectations for how quickly reviews should be completed (e.g., peer reviews in 1 day, senior reviews in 2 days).
• Rotate Peer Reviewers: Encourage team members to review code from other projects to foster cross-functional knowledge.
• Document Standards: Maintain a central document for coding standards and architectural principles to guide both peer and senior reviewers.

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Conclusion

The two-step code review process provides a scalable framework for ensuring code quality and consistency in large teams. By engaging peers in functional reviews and senior developers in architectural oversight, you create a balanced system that improves code, reduces bottlenecks, and fosters growth across the team.

Start small—implement peer and senior reviews on a few critical projects, then expand as your team adapts to the process. With time, this layered approach will become second nature, strengthening your codebase and your team.

What strategies have worked for your team in scaling code reviews? Share your experiences in the comments below!