Code review checklist for LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Key focus areas in a Low-Level Design (LLD) code review

Which of the following is NOT typically a focus area during a code review of Low-Level Design?

A Ensuring proper error handling and logging mechanisms

B Verifying the correctness of database schema design

C Checking if the code follows the defined class and method structure

D Reviewing adherence to naming conventions and code readability

💡 Hint

Think about what LLD focuses on versus higher-level design aspects.

Database schema design is usually part of high-level design or database design, not LLD code review.

❓ Architecture

intermediate

Identifying design pattern usage in LLD during code review

During a code review of LLD, which option best describes how to verify correct use of design patterns?

A Verify that design patterns are implemented as per their standard structure and intent

B Check if the code uses design patterns only if explicitly mentioned in requirements

C Ensure all classes inherit from a single base class regardless of pattern

D Confirm that design patterns are avoided to keep code simple

💡 Hint

Design patterns have specific structures and purposes.

Correct use of design patterns means implementing them according to their standard definitions and intent.

❓ scaling

advanced

Evaluating scalability considerations in LLD code review

Which option best describes a scalability concern to check during LLD code review?

A Verifying that all methods are static to avoid object creation overhead

B Confirming that the code uses synchronous calls exclusively for simplicity

C Ensuring that classes and methods are designed to handle increased load without bottlenecks

D Checking if the code uses global variables extensively for faster access

💡 Hint

Think about how design affects handling more users or data.

Scalability in LLD means designing classes and methods to efficiently handle growth in load.

❓ tradeoff

advanced

Tradeoff analysis in LLD code review

Which tradeoff is important to evaluate during LLD code review?

A Selecting between different font styles for code editors

B Choosing between detailed comments and code brevity

C Deciding whether to use tabs or spaces for indentation

D Balancing between code modularity and performance overhead

💡 Hint

Consider design decisions that affect both maintainability and speed.

Tradeoffs in LLD often involve balancing modularity (easy maintenance) with performance (speed).

❓ component

expert

Determining the correctness of component interactions in LLD

In a code review of LLD, how can you best verify that component interactions are correctly designed?

A Ensure components communicate only through well-defined interfaces or APIs

B Check if components directly access each other's private data fields

C Verify that all components are merged into a single monolithic class

D Confirm that components use global state variables for sharing data

💡 Hint

Good design isolates components and controls their communication.

Correct component interaction means using clear interfaces to avoid tight coupling and maintain encapsulation.

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