How To Approach

• How To Approach
  • 1. Outline use cases, constraints and assumptions
  • 2. Create a high level design
  • 3. Design core components
  • 4. Scale the design

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

You can use the following steps to guide the discussion. As an exercise, you can work through system design interview questions with solutions using these steps.

1. Outline use cases, constraints, and assumptions.

2. Create a high level design.

3. Design core components.

4. Scale the design.

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 a 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

3. Design core components

Dive into details for each core component.

For example, if you were asked to design a url shortening service, discuss:

• Generating and storing a hash of the full url
  • MD5 and Base62
  • Hash collisions
  • SQL or NoSQL
  • Database schema
• Translating a hashed url to the full url
  • Database lookup
• API and object-oriented design

4. Scale the design

Identify and address bottlenecks using principles of scalable system design, given the constraints.

For example, do you need the following to address scalability issues?

• Load balancer
• Horizontal scaling
• Caching
• Database sharding

Discuss potential solutions and trade-offs. Everything is a trade-off.