Code review checklist for LLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the primary goal of a Low-Level Design (LLD) code review?

To ensure the detailed design and implementation meet the requirements, are clear, maintainable, and follow best practices.

beginner

Name two key aspects to check in class and method design during an LLD code review.

Check for single responsibility principle and proper method naming that clearly describes functionality.

intermediate

Why is it important to review error handling and logging in LLD code reviews?

Because proper error handling ensures system stability and logging helps in debugging and monitoring.

intermediate

What should you verify about data structures and algorithms in an LLD code review?

Verify that chosen data structures and algorithms are efficient and appropriate for the problem.

beginner

How does adherence to coding standards impact the LLD code review?

It improves code readability, consistency, and maintainability across the project.

Which principle should be checked to ensure a class has one clear responsibility?

A Open/Closed Principle

B Liskov Substitution Principle

C Single Responsibility Principle

D Dependency Inversion Principle

The Single Responsibility Principle states that a class should have only one reason to change.

What is a key reason to review method names in LLD?

A To ensure they are short and cryptic

B To ensure they are all uppercase

C To ensure they use numbers for uniqueness

D To ensure they clearly describe the method's functionality

Clear method names improve code readability and understanding.

Why should error handling be reviewed in LLD?

A To ignore exceptions

B To ensure graceful handling and recovery from errors

C To ensure the system crashes on errors

D To remove all try-catch blocks

Proper error handling helps maintain system stability and user experience.

Which of the following is NOT a focus during LLD code review?

A UI design

B Algorithm efficiency

C Data structure appropriateness

D Code readability

UI design is typically reviewed in higher-level design or frontend reviews, not LLD.

Adhering to coding standards helps with:

A Improving code consistency and maintainability

B Increasing bugs

C Making code harder to read

D Slowing down development

Coding standards promote uniformity and easier maintenance.

List the main areas to focus on during a Low-Level Design code review.

Think about what makes code clear, efficient, and reliable.

Explain why reviewing error handling and logging is critical in LLD.

Consider what happens when things go wrong in the system.

Practice

1. Which of the following is the MOST important focus when reviewing a Low-Level Design (LLD) document?

easy

A. Clarity and correctness of the design

B. The color scheme of the document

C. The number of pages in the document

D. The font style used

Solution

1. Step 1: Understand the purpose of LLD review

   The main goal is to ensure the design is clear and correct so developers can implement it properly.

2. Step 2: Evaluate options based on relevance

   Options A, B, and D relate to formatting, which is less critical than clarity and correctness.

3. Final Answer:

   Clarity and correctness of the design -> Option A

4. Quick Check:

   Focus on clarity and correctness = C [OK]

Hint: Focus on design clarity and correctness first [OK]

Common Mistakes:

• Focusing on document style over content
• Ignoring correctness for aesthetics
• Confusing LLD with high-level design

2. Which checklist item should be included to ensure modularity in an LLD review?

easy

A. Ensure the document has a table of contents

B. Check if the design uses consistent variable names

C. Count the total number of classes

D. Verify if components have clear, single responsibilities

Solution

1. Step 1: Understand modularity in design

   Modularity means breaking the system into parts that each do one thing well.

2. Step 2: Match options to modularity

   Verify if components have clear, single responsibilities directly relates to single responsibility, a key modularity principle. Others are unrelated.

3. Final Answer:

   Verify if components have clear, single responsibilities -> Option D

4. Quick Check:

   Modularity = single responsibility components [OK]

Hint: Look for single responsibility to ensure modularity [OK]

Common Mistakes:

• Confusing naming consistency with modularity
• Counting classes without checking responsibilities
• Focusing on document formatting

3. Given this checklist item: "Ensure all public methods have clear input and output definitions." What is the MOST likely outcome if this is NOT followed?

medium

A. Developers may implement methods incorrectly due to unclear contracts.

B. The system will automatically generate method documentation.

C. The code will run faster.

D. The design will have fewer classes.

Solution

1. Step 1: Understand the role of input/output definitions

   Clear definitions guide developers on how to use methods correctly.

2. Step 2: Analyze consequences of missing definitions

   Without clear contracts, developers may misunderstand method usage, causing errors.

3. Final Answer:

   Developers may implement methods incorrectly due to unclear contracts. -> Option A

4. Quick Check:

   Unclear method contracts = incorrect implementation [OK]

Hint: Clear method contracts prevent implementation errors [OK]

Common Mistakes:

• Assuming code runs faster without definitions
• Thinking documentation is auto-generated
• Confusing method count with clarity

4. You find a design where security considerations are missing in the LLD. What is the BEST immediate action during the code review?

medium

A. Approve the design since security is handled later.

B. Ignore security as it is not part of LLD.

C. Request adding security checks and data validation in the design.

D. Suggest removing modularity to simplify security.

Solution

1. Step 1: Recognize importance of security in LLD

   Security should be considered early to avoid costly fixes later.

2. Step 2: Choose action that improves design quality

   Requesting security checks and validation ensures design is robust and safe.

3. Final Answer:

   Request adding security checks and data validation in the design. -> Option C

4. Quick Check:

   Missing security = request additions [OK]

Hint: Always include security early in design reviews [OK]

Common Mistakes:

• Ignoring security until later stages
• Approving incomplete designs
• Removing modularity harms security

5. During a code review for a complex LLD, you notice the design lacks scalability considerations and testability is weak. Which combined checklist items should you prioritize to improve the design?

hard

A. Increase code comments and skip testing details.

B. Add modular components with clear interfaces and include unit test plans.

C. Focus only on UI design and ignore backend scalability.

D. Reduce the number of classes and remove error handling.

Solution

1. Step 1: Identify key improvements for scalability and testability

   Modular components with clear interfaces help scale and isolate parts for testing.

2. Step 2: Match checklist items to these improvements

   Including unit test plans ensures testability is addressed alongside modularity.

3. Final Answer:

   Add modular components with clear interfaces and include unit test plans. -> Option B

4. Quick Check:

   Modularity + testing plans = better scalability and testability [OK]

Hint: Combine modularity and testing for scalable, testable design [OK]

Common Mistakes:

• Removing error handling weakens design
• Ignoring backend scalability
• Focusing only on comments without tests