Learn how to design large-scale systems. Prep for the system design interview. Includes Anki flashcards.
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The System Design Primer


Motivation

Learn how to design large scale systems from the open source community.

Understand real-world architectures.

Prep for the system design interview.

Learn how to design large scale systems

Learning how to design scalable systems will make you a better engineer.

System design is a broad topic. There is a vast amount of resources scattered throughout the web on system design principles.

This repo is an organized collection of resources to help you learn how to build systems at scale.

Topics for learning system design:

Learn from the open source community

This is an early draft of a continually updated, open source project.

Contributions are welcome!

Prep for the system design interview

In addition to coding interviews, system design is a required component of the technical interview process at many tech companies.

Practice common system design interview questions and compare your results with sample discussions, code, and diagrams.

Additional topics for interview prep:

For interviews, do I need to know everything here?

No, you don't need to know everything here to prepare for the interview.

What you are asked in an interview depends on variables such as:

  • How much experience you have
  • What your technical background is
  • What positions you are interviewing for
  • Which companies you are interviewing with
  • Luck

More experienced candidates are generally expected to know more about system design. Architects or team leads might be expected to know more than individual contributors. Top tech companies are likely to have one or more design interview rounds.

Any resources to prep for coding interviews?

Check out the sister repo interactive-coding-challenges for coding interview resources.

Contributing

Learn from the community.

Feel free to submit pull requests to help:

  • Fix errors
  • Improve sections
  • Add new sections

Content that needs some polishing is placed under development.

Review the Contributing Guidelines.

Index of system design topics

Summaries of various system design topics, including pros and cons. Everything is a trade-off.

Each section contains links to more in-depth resources.

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Study guide

Suggested topics to review based on your interview timeline (short, medium, long).

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Start broad and go deeper in a few areas. It helps to know a little about various key system design topics. Adjust the following guide based on your experience, what positions you are interviewing for, and which companies you are interviewing with.

  • Short - Aim for breadth with system design topics. Practice by solving some interview questions.
  • Medium - Aim for breadth and some depth with system design topics. Practice by solving a many interview questions.
  • Long - Aim for breadth and more depth with system design topics. Practice by solving a most interview questions.
Short Medium Long
Read through the System design topics to get a broad understanding of how systems work 👍 👍 👍
Read through a few articles in the Company engineering blogs for the companies you are interviewing with 👍 👍 👍
Read through a few Real world architectures 👍 👍 👍
Review How to approach a system design interview question 👍 👍 👍
Work through System design interview questions with solutions Some Many Most
Work through Object-oriented design interview questions with solutions Some Many Most
Review Additional system design interview questions Some Many Most

How to approach a system design interview question

How to tackle a system design interview question.

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. To help solidify this process, work through the System design interview questions with solutions section using the following steps.

Step 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?

Step 2: Create a high level design

Outline a high level design with all important components.

  • Sketch the main components and connections
  • Justify your ideas

Step 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

Step 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 scaling
  • Caching
  • Database sharding

Discuss potential solutions and trade-offs. Everything is a trade-off. Address bottlenecks using principles of scalable system design.

Back-of-the-envelope calculations

You might be asked to do some estimates by hand. Refer to the Appendix for the following resources:

Source(s) and further reading

Check out the following links to get a better idea of what to expect:

System design interview questions with solutions

Common system design interview questions with sample discussions, code, and diagrams.

Solutions linked to content in the solutions/ folder.

Question
Design Pastebin.com (or Bit.ly) Solution
Design the Twitter timeline (or Facebook feed)
Design Twitter search (or Facebook search)
Solution
Design a web crawler Solution
Design Mint.com Solution
Design the data structures for a social network Solution
Design a key-value store for a search engine Solution
Design Amazon's sales ranking by category feature Solution
Design a system that scales to millions of users on AWS Solution
Add a system design question Contribute

Design Pastebin.com (or Bit.ly)

View exercise and solution

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View exercise and solution

Imgur

Design a web crawler

View exercise and solution

Imgur

Design Mint.com

View exercise and solution

Imgur

Design the data structures for a social network

View exercise and solution

Imgur

Design a key-value store for a search engine

View exercise and solution

Imgur

Design Amazon's sales ranking by category feature

View exercise and solution

Imgur

Design a system that scales to millions of users on AWS

View exercise and solution

Imgur

Object-oriented design interview questions with solutions

Common object-oriented design interview questions with sample discussions, code, and diagrams.

Solutions linked to content in the solutions/ folder.

Note: This section is under development

Question
Design a deck of cards to be used for blackjack Solution
Design a call center Solution
Design a hash map Solution
Design a least recently used cache Solution
Design a parking lot Solution
Design a chat server Solution
Design a circular array Contribute
Add an object-oriented design question Contribute