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Code Review - Interview Questions & Answers

Master Code Reviews with interview-focused questions and answers. Learn code review objectives, review checklists, pull requests, clean code practices, security reviews, and enterprise review standards with Java examples.

Introduction

Code Review is one of the most important software engineering practices in modern development teams.

Before code reaches production, experienced developers review it to ensure it is:

  • Correct
  • Secure
  • Maintainable
  • Readable
  • Efficient
  • Production Ready

Companies like Google, Amazon, Microsoft, Netflix, and Meta require code reviews before merging pull requests.

Why Interviewers Ask About Code Reviews?

Interviewers want to evaluate whether you can:

  • Write maintainable code
  • Identify bugs before production
  • Collaborate effectively
  • Follow coding standards
  • Improve software quality

Senior developers are expected to review code, mentor teammates, and improve engineering quality.

flowchart LR

Developer --> PullRequest

PullRequest --> CodeReview

CodeReview --> Approved

Approved --> Production

Interview Question 1

What is Code Review?

Answer

Code Review is the process of examining another developer's code before it is merged into the main branch.

The goal is to improve:

  • Code Quality
  • Readability
  • Security
  • Performance
  • Maintainability

It also helps teams share knowledge and maintain consistent coding standards.

Diagram

flowchart LR

Developer --> PullRequest

PullRequest --> Reviewer

Reviewer --> Feedback

Feedback --> Merge

Java Example

Instead of reviewing only whether code compiles:

public double calculateDiscount(double price) {
    return price * 0.10;
}

Reviewers should also ask:

  • Is the method name meaningful?
  • Should the discount value be configurable?
  • Are edge cases handled?
  • Is validation required?

Interview Tip

A strong interview answer:

Code Review is a collaborative process that improves software quality before deployment.

Interview Question 2

Why is Code Review important?

Answer

Code Reviews help teams:

  • Detect bugs early
  • Improve code quality
  • Reduce technical debt
  • Improve consistency
  • Share knowledge
  • Improve security
  • Reduce production incidents

Diagram

mindmap
  root((Code Review))
    Better Quality
    Security
    Knowledge Sharing
    Readability
    Maintainability
    Fewer Bugs

Real Example

A reviewer notices that an API exposes customer passwords in logs.

Finding this during review prevents a serious production security issue.

Interview Tip

Mention that fixing bugs during review is much cheaper than fixing production defects.

Interview Question 3

What should you check during a Code Review?

Answer

A good reviewer checks multiple aspects of the code.

Functional Review

  • Does the code solve the problem?
  • Are business rules implemented correctly?

Readability

  • Meaningful names
  • Small methods
  • Simple logic

Performance

  • Avoid unnecessary loops
  • Database optimization
  • Efficient algorithms

Security

  • SQL Injection
  • Input validation
  • Sensitive data exposure

Testing

  • Unit tests
  • Edge cases
  • Error scenarios

Diagram

flowchart TD

CodeReview --> Functionality

CodeReview --> Readability

CodeReview --> Performance

CodeReview --> Security

CodeReview --> Testing

Interview Tip

Don't review only the syntax.

Review the design and business logic as well.

Interview Question 4

What is a Pull Request (PR)?

Answer

A Pull Request is a request to merge code changes into another branch.

Typical Pull Request Workflow:

  1. Developer creates feature branch.
  2. Code is committed.
  3. Pull Request is created.
  4. Reviewer reviews code.
  5. Changes are requested if necessary.
  6. Code is approved.
  7. Changes are merged.

Diagram

flowchart LR

FeatureBranch --> Commit

Commit --> PullRequest

PullRequest --> Review

Review --> Approval

Approval --> Merge

Merge --> MainBranch

Interview Tip

A Pull Request should be:

  • Small
  • Easy to review
  • Well documented
  • Focused on one feature

Interview Question 5

What makes a Good Code Review?

Answer

A good review focuses on improving the code, not criticizing the developer.

Characteristics of a good review:

  • Respectful feedback
  • Clear explanations
  • Constructive suggestions
  • Business-focused discussions
  • Consistent coding standards

Example Feedback

❌ Bad

This code is wrong.

✅ Good

This logic works correctly.

Consider extracting the validation into a separate method to improve readability and make unit testing easier.

Diagram

flowchart LR

Reviewer --> ConstructiveFeedback

ConstructiveFeedback --> BetterCode

BetterCode --> TeamLearning

Interview Tip

Review the code, not the developer.

Always explain why a suggested change improves the code.

Interview Question 6

What are the Common Code Review Mistakes?

Answer

A reviewer should focus on improving the software, not criticizing the developer.

Common mistakes include:

  • Reviewing only coding style
  • Ignoring business logic
  • Missing security issues
  • Missing performance problems
  • Reviewing very large Pull Requests
  • Giving unclear feedback
  • Approving code without testing

Diagram

flowchart TD

CodeReview --> StyleOnly

CodeReview --> IgnoreLogic

CodeReview --> IgnoreSecurity

CodeReview --> IgnorePerformance

CodeReview --> LargePR

CodeReview --> PoorFeedback

Interview Tip

Review the correctness, design, and maintainability before commenting on formatting.

Interview Question 7

What should be checked from a Security perspective?

Answer

Security should always be part of every code review.

Review checklist:

  • Input validation
  • SQL Injection
  • XSS vulnerabilities
  • Authentication
  • Authorization
  • Password encryption
  • Sensitive data logging
  • API security
  • Secret management

Bad Example

String sql =
"SELECT * FROM USERS WHERE ID=" + id;

Good Example

PreparedStatement ps =
connection.prepareStatement(

    "SELECT * FROM USERS WHERE ID=?"

);

ps.setInt(1, id);

Diagram

flowchart LR

UserInput --> Validation

Validation --> SecureCode

SecureCode --> Database

Interview Tip

Always ask:

Can an attacker misuse this code?

Interview Question 8

What should be checked from a Performance perspective?

Answer

Performance reviews ensure the application scales efficiently.

Review checklist:

  • Nested loops
  • N+1 Database Queries
  • Unnecessary object creation
  • Memory usage
  • Database indexes
  • API response time
  • Expensive computations
  • Proper caching

Bad Example

for(Customer customer : customers){

    database.findOrders(customer.getId());

}

N database calls.

Better Example

Map<Long,List<Order>> orders =
orderRepository.findAllOrders();

Single database call.

Diagram

flowchart LR

Application --> Database

Database --> MultipleQueries

MultipleQueries --> SlowResponse

Database --> OptimizedQuery

OptimizedQuery --> FastResponse

Interview Tip

Performance issues discovered during code review are much cheaper to fix than after deployment.

Interview Question 9

What tools are commonly used during Code Reviews?

Answer

Modern teams use automated tools together with manual reviews.

Common tools:

Tool Purpose
GitHub Pull Requests
GitLab Merge Requests
Bitbucket Code Reviews
SonarQube Code Quality
Checkstyle Coding Standards
PMD Static Analysis
SpotBugs Bug Detection

Diagram

flowchart LR

Developer --> PullRequest

PullRequest --> GitHub

GitHub --> SonarQube

SonarQube --> Reviewer

Reviewer --> Approval

Interview Tip

Automation finds repetitive issues.

Human reviewers focus on:

  • Business logic
  • Architecture
  • Maintainability

Interview Question 10

What are Code Review Best Practices?

Answer

Follow these best practices:

  • Keep Pull Requests small.
  • Review code daily.
  • Explain review comments clearly.
  • Focus on code quality.
  • Check business logic.
  • Verify security.
  • Review performance.
  • Ensure unit tests exist.
  • Follow coding standards.
  • Be respectful and constructive.

Diagram

mindmap
  root((Best Practices))
    Small PRs
    Readability
    Security
    Performance
    Testing
    Documentation
    Coding Standards
    Respectful Feedback

Interview Tip

Good reviews improve both the codebase and the engineering team.

Common Interview Mistakes

  • Reviewing only formatting.
  • Ignoring business requirements.
  • Missing null checks.
  • Ignoring exception handling.
  • Not reviewing unit tests.
  • Ignoring SQL performance.
  • Approving code without understanding it.
  • Giving personal instead of technical feedback.

Quick Revision

Concept Key Point
Code Review Improves software quality before merge
Pull Request Request to merge code changes
Readability Easy to understand code
Security Validate inputs and protect sensitive data
Performance Review algorithms and database access
Testing Ensure unit and integration tests exist
SonarQube Static code quality analysis
Small PRs Easier to review and safer to merge
Constructive Feedback Improve the code, not criticize the developer
Best Practice Review functionality, design, security, and maintainability together

Interviewer's Expectations

Junior Java Developer

  • Understand the purpose of code reviews.
  • Create clean Pull Requests.
  • Follow coding standards.
  • Accept feedback positively.

Senior Java Developer

  • Identify design issues.
  • Review security and performance.
  • Mentor team members through constructive feedback.
  • Ensure production readiness.

Solution Architect

  • Define organization-wide code review standards.
  • Establish secure coding guidelines.
  • Integrate automated quality gates.
  • Promote engineering excellence through review culture.
  • Balance quality, delivery speed, and maintainability.

Related Interview Questions

  • What is Clean Code?
  • What is Technical Debt?
  • What is Refactoring?
  • What is Static Code Analysis?
  • What is SonarQube?
  • What are SOLID Principles?
  • What is Pair Programming?
  • How do you review a Pull Request?
  • What is Secure Coding?
  • What is CI/CD Quality Gate?

Summary

Code Reviews are a fundamental engineering practice that helps teams improve software quality, security, performance, and maintainability before code reaches production. A successful review goes beyond checking syntax—it validates business logic, architecture, testing, and operational readiness.

For interviews, demonstrate that you understand what to review, why it matters, and how to provide constructive feedback. Mention automated tools such as SonarQube, emphasize security and performance considerations, and explain how effective code reviews reduce technical debt and production incidents. This practical perspective is highly valued in senior Java developer and solution architect interviews.