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.

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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