LLD interview expectations - System Design Exercise

Design: Low-Level Design Interview Preparation

Covers typical LLD interview expectations including design approach, communication, and coding style. Does not cover specific coding problems or system design at large scale.

Functional Requirements

FR1: Understand common expectations in LLD interviews

FR2: Identify key components and design principles to demonstrate

FR3: Prepare to explain design decisions clearly

FR4: Show ability to write clean, modular, and scalable code

FR5: Demonstrate knowledge of design patterns and best practices

Non-Functional Requirements

NFR1: Focus on clarity and simplicity in design

NFR2: Use industry best practices

NFR3: Designs should be scalable and maintainable

NFR4: Time-limited interview setting (typically 30-45 minutes)

Think Before You Design

Questions to Ask

❓ Question 1

❓ Question 2

❓ Question 3

❓ Question 4

❓ Question 5

❓ Question 6

Key Components

Classes and objects representing entities

Interfaces and abstractions

Methods and their responsibilities

Data structures used internally

Error handling and validation

Modularity and separation of concerns

Design Patterns

Factory pattern for object creation

Singleton for shared resources

Observer for event handling

Strategy for interchangeable algorithms

Decorator for extending functionality

MVC or layered architecture for separation

Reference Architecture

LLD Interview Preparation
+-------------------------+
| Understand Requirements |
+-----------+-------------+
            |
            v
+-------------------------+
| Identify Key Entities    |
+-----------+-------------+
            |
            v
+-------------------------+
| Define Classes & Methods |
+-----------+-------------+
            |
            v
+-------------------------+
| Apply Design Patterns    |
+-----------+-------------+
            |
            v
+-------------------------+
| Write Clean, Modular Code|
+-------------------------+

Components

Requirement Analysis

N/A

Understand problem scope and constraints

Entity Modeling

UML or simple class diagrams

Identify main objects and their relationships

Class Design

Object-oriented programming

Define classes, methods, and responsibilities

Design Patterns

Common OOP patterns

Use reusable solutions for common problems

Code Implementation

Programming language of choice

Write modular, readable, and testable code

Communication

Verbal explanation

Explain design decisions clearly to interviewer

Request Flow

1. Start by clarifying requirements with the interviewer

2. Identify key entities and their attributes

3. Define classes and their methods based on responsibilities

4. Choose appropriate design patterns to simplify design

5. Write code focusing on modularity and clarity

6. Explain each step and justify design choices

7. Handle edge cases and error scenarios

8. Iterate based on feedback or questions

Database Schema

Not applicable for general LLD interview expectations; focus is on class design and object relationships rather than database.

Scaling Discussion

Bottlenecks

Overcomplicating design with unnecessary patterns

Poor communication leading to misunderstood requirements

Writing monolithic code without modularity

Ignoring edge cases and error handling

Not considering scalability or maintainability

Solutions

Keep design simple and focused on requirements

Ask clarifying questions frequently

Break down code into small, reusable components

Include error handling and validation in design

Discuss how design can evolve for scalability

Interview Tips

Time: Spend first 5-10 minutes clarifying requirements and asking questions, next 20-25 minutes designing and coding, last 5-10 minutes explaining and refining design.

Clarify requirements before starting design

Explain your thought process clearly

Use simple and modular class structures

Apply relevant design patterns appropriately

Write clean and readable code

Discuss trade-offs and alternatives

Show awareness of scalability and maintainability