4 Steps to crack your next System Design Interview

The system design interview is an open-ended conversation. You are expected to lead it.

To help solidify this process, You can use the following steps to guide the discussion.

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1. Outline use cases, constraints, and assumptions

Gather requirements and scope the problem. Ask questions to clarify use cases and constraints. Discuss assumptions.

• Who is going to use it?
• How are they going to use it?
• How many users are there?
• What does the system do?
• What are the inputs and outputs of the system?
• How much data do we expect to handle?
• How many requests per second do we expect?
• What is the expected read to write ratio?

2. Create a high-level design

Outline a high-level design with all important components.

• Sketch the main components and connections
• Justify your ideas

Example:

3. Design core components

Dive into details for each core component. For example, if you were asked to design an Instagram like website, discuss things in detail for each module:

Example :

- User Authentication & Authorization module

1. Login / Signup Flows.
2. How the user will be authenticated/authorized when he log in and try to access your application.
3. Database Schema
4. What is your choice of the database? (SQL or NoSQL)
5. API and object-oriented design

- Timeline Module

1. How user timeline will be shown based on his follows.
2. Database Schema
3. What is your choice of database? (SQL or NOSQL)
4. API and object-oriented design

Always give preference to complete the high-level design of end-to-end user flows for the given problem statement. Pick a couple of modules from your design and try to deep dive into it by explaining the low-level design.

4. Scale the design

Identify and address bottlenecks, given the constraints. For example, do you need the following to address scalability issues?

• Load balancer
• Horizontal vs Vertical scaling
• Caching
• Database sharding

Discuss potential solutions and trade-offs. Address bottlenecks if any.

Most Common System Design Questions

1. Design URL shortening service like bit.ly
2. Design Social network like Facebook/Twitter/Instagram.
3. Design Cab booking system like Uber.
4. Design a Web Crawler.
5. Design Video Streaming Service like Youtube.
6. Design a system like Quora/Reddit.
7. Design ticket booking system like Ticketmaster

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