Learning code review

What is a Code Review?

A code review is the process of systematically examining source code written by a developer to identify mistakes, improve quality, and ensure adherence to coding standards. It is a peer-based activity where one or more team members review the code before it is merged into the main codebase.

History of Code Review

The concept of code review dates back to the early days of software engineering in the 1970s, when formal inspections were introduced by Michael Fagan at IBM. These inspections were strict, document-driven, and involved structured meetings. Over time, the practice evolved into more lightweight and flexible processes, especially with the rise of Agile and open-source development, where code review became a standard part of daily workflows.

Importance of Code Review

Code reviews are critical in modern software development. They:

  • Improve code quality and maintainability
  • Detect bugs early in the development cycle
  • Facilitate knowledge sharing among developers
  • Encourage collaboration and collective ownership of the code
  • Enforce coding standards and best practices

Components of a Code Review

A successful code review process usually involves:

  • Author: The developer who wrote the code.
  • Reviewers: Team members who evaluate the code.
  • Tools: Platforms such as GitHub, GitLab, Bitbucket, or specialized review tools.
  • Guidelines: Coding standards, project-specific conventions, and review checklists.
  • Feedback: Constructive comments, suggestions, and clarifications.

How to Perform a Code Review

  • Start by understanding the purpose of the code changes.
  • Review smaller code changes instead of very large pull requests.
  • Check for correctness, readability, performance, and security.
  • Ensure the code follows style guides and project conventions.
  • Provide clear, respectful, and actionable feedback.
  • Encourage discussion instead of one-sided judgment.

Is There a Formal Process?

Yes, organizations often define formal processes for code reviews. A typical process may include:

  1. Developer submits code changes (pull request or merge request).
  2. Automated tests and linters run first.
  3. One or more reviewers analyze the code and leave comments.
  4. The author addresses feedback and makes changes.
  5. Reviewers approve the changes.
  6. Code is merged into the main branch.

Some teams also use pair programming or walkthroughs as part of the process.

Important Details to Pay Attention To

Reviewers should pay attention to:

  • Logic and correctness of the code
  • Security vulnerabilities
  • Performance implications
  • Readability and maintainability
  • Compliance with coding standards
  • Proper documentation and comments

While it’s important to catch issues, reviewers should avoid nitpicking too much on trivial details unless they affect the project long-term.

How Much Time Should We Spend?

Research suggests that effective code reviews should be 30 to 60 minutes per session, focusing on chunks of code not exceeding 400 lines at a time. Longer reviews often reduce effectiveness due to reviewer fatigue. The key is consistency—review regularly, not occasionally.

Applying Code Review in Current Projects

To integrate code reviews into your development process:

  • Use pull requests as the entry point for reviews.
  • Automate tests to catch basic issues before review.
  • Define clear review guidelines for your team.
  • Encourage collaborative discussions.
  • Use tools like GitHub, GitLab, or Bitbucket that integrate seamlessly with workflows.
  • Monitor review metrics (time spent, defects found, review coverage) to improve efficiency.