Code review checklist for LLD - System Design Exercise

Design: Code Review Checklist for Low-Level Design (LLD)

Focus on reviewing low-level design diagrams and documents. Out of scope: code syntax, high-level architecture, deployment details.

Functional Requirements

FR1: Ensure design correctness and completeness

FR2: Verify adherence to design principles and patterns

FR3: Check for scalability and performance considerations

FR4: Validate modularity and separation of concerns

FR5: Confirm clarity and maintainability of design

FR6: Identify potential security and error handling gaps

FR7: Ensure consistency with overall system architecture

Non-Functional Requirements

NFR1: Checklist must be applicable to designs of varying complexity

NFR2: Must be easy to use by both junior and senior engineers

NFR3: Should cover both functional and non-functional aspects

NFR4: Checklist items must be clear and actionable

Think Before You Design

Questions to Ask

❓ Question 1

❓ Question 2

❓ Question 3

❓ Question 4

❓ Question 5

❓ Question 6

❓ Question 7

Key Components

Class and object diagrams

Sequence and interaction diagrams

Data models and schemas

Interfaces and APIs

Error handling mechanisms

Security controls

Performance optimization techniques

Design Patterns

Single Responsibility Principle

Open/Closed Principle

Factory and Builder patterns

Observer and Strategy patterns

Layered architecture

Dependency Injection

Fail-safe and retry mechanisms

Reference Architecture

 +---------------------+       +---------------------+       +---------------------+
 |  Design Document     | ----> |  Review Checklist    | ----> |  Feedback & Updates  |
 +---------------------+       +---------------------+       +---------------------+

Components

Design Document

LLD diagrams and documents

Contains detailed low-level design including classes, methods, and interactions

Review Checklist

Structured checklist template

Guides reviewers through key design aspects to verify correctness and quality

Feedback & Updates

Collaboration tools (e.g., comments, issue trackers)

Captures review feedback and tracks design improvements

Request Flow

1. Designer creates or updates the low-level design document.

2. Reviewer uses the checklist to systematically evaluate the design.

3. Reviewer notes issues or suggestions based on checklist items.

4. Feedback is communicated back to the designer.

5. Designer revises the design accordingly.

6. Cycle repeats until design meets quality standards.

Database Schema

Not applicable as this is a process checklist rather than a data-driven system.

Scaling Discussion

Bottlenecks

Checklist becomes too long or complex, reducing usability.

Inconsistent application of checklist by different reviewers.

Difficulty in tracking feedback and design iterations at scale.

Solutions

Prioritize checklist items to focus on critical design aspects.

Provide training and examples to standardize review approach.

Use integrated collaboration tools to manage feedback and version control.

Interview Tips

Time: Spend 10 minutes explaining the checklist purpose and key items, 15 minutes walking through example review scenarios, and 5 minutes discussing scaling and tooling.

Importance of systematic design review to catch issues early.

Balancing thoroughness with usability in checklist design.

How checklist supports maintainability, scalability, and security.

Role of collaboration and feedback in improving designs.

Adapting checklist for different project sizes and teams.