Checklist for doing a code review
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Code Review

Phase 1: The Light Pass


  • Code formatting has been used
  • Line indentation char and line breaks
  • Only required files are changed
  • Disagreement between code and specification
  • Comments in source code are included
  • Documentation of the implementation is created or updated
  • Does not contain any unimplemented areas like //TODO or //FIXME
  • Optimistic or undefensive programming

Unclear Or Messy

  • Verify correct and meaningful naming
  • Magic numbers and values
  • Variables used for more than one purpose
  • Minimized variable, method and class scopes
  • Method signature
  • Packing too much into one line
  • Complex IF conditions, IF instead of Switch
  • Cyclomatic complexity

Error Handling

  • Use exceptions only for unexpected errors
  • Avoid empty catch blogs
  • Error handler over-catches exceptions and aborts current flow or application
  • Error handler is not implemented e.g. contains TODO, FIXME


  • Review class imports
  • Wrong use of == and equals()
  • Wrong use of collection data types, like List instead of Set
  • Object contract errors (e.g. equals and hashCode)
  • Exposure to immutable data types

Git Commit Message

  • Describes what and why it has changed
  • Verify correct format

Phase 2: The Contextual Pass

Functional programming

  • Prefer immutability
  • Minimize side-effects and perform them in a central place
  • Do not rely on global state
  • Plan for composing functions
  • Keep method signatures as simple as possible
  • Write generic functions
  • Avoid type specific functions

Code Structure

  • Understandability of written changes
  • No logical errors
  • Max usage of static type compiler checking
  • Does not violate architecture guidelines, design principles or implementation patterns
  • Are there any alternative implementations that increase simplicity, readability or maintainability
  • Check edge cases in functions
  • Any better approach to use a framework, library or class exists?
  • Look for omissions: Shouldn't this component also do X?
  • Enough log statements to find bugs quickly

External Systems

  • Reduce amount of calls / Optimize calls to external systems


  • Unit-tests and End 2 End Tests are added and test all functionality
  • Test coverage of changed lines and critical path

Code-Review Commenting

  • Adding comments: Be polite and constructive
  • Add positive comments for good code e.g. unusually elegant solution, creative solution, great design


  • Sign of the pull request


Code Review

Code Briefing: What does it mean when code is “easy to reason about”?

Do Not Allow Bad Smells In Your Code

Writing Great Git Commit Messages; A Revision

Giving better code reviews

Coding like Shakespeare: practical function naming conventions

Simple Testing Can Prevent Most Critical Failures: An Analysis of Production Failures in Distributed Data-Intensive Systems

Software Architecture and Design

YouTube: Core Design Principles for Software Developers

Information about properly formatted commit messages

Replacing Throwing Exceptions with Notification in Validations

The Dao of Immutability