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The System Design Primer
Motivation
Learn how to design large-scale systems.
Prep for the system design interview.
Learn how to design large-scale systems
Learning how to design scalable systems will help you become 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.
Learn from the open source community
This is 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 solutions: discussions, code, and diagrams.
Additional topics for interview prep:
- Study guide
- How to approach a system design interview question
- System design interview questions, with solutions
- Object-oriented design interview questions, with solutions
- Additional system design interview questions
Anki flashcards
The provided Anki flashcard decks use spaced repetition to help you retain key system design concepts.
Great for use while on-the-go.
Coding Resource: Interactive Coding Challenges
Looking for resources to help you prep for the Coding Interview?
Check out the sister repo Interactive Coding Challenges, which contains an additional Anki deck:
Contributing
Learn from the community.
Feel free to submit pull requests to help:
- Fix errors
- Improve sections
- Add new sections
- Translate
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.
- System design topics: start here
- Performance vs scalability
- Latency vs throughput
- Availability vs consistency
- Consistency patterns
- Availability patterns
- Domain name system
- Content delivery network
- Load balancer
- Reverse proxy (web server)
- Application layer
- Database
- Cache
- Asynchronism
- Communication
- Security
- Appendix
- Under development
- Credits
- Contact info
- License
Study guide
Suggested topics to review based on your interview timeline (short, medium, long).
Q: For interviews, do I need to know everything here?
A: 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.
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 timeline, experience, what positions you are interviewing for, and which companies you are interviewing with.
- Short timeline - Aim for breadth with system design topics. Practice by solving some interview questions.
- Medium timeline - Aim for breadth and some depth with system design topics. Practice by solving many interview questions.
- Long timeline - Aim for breadth and more depth with system design topics. Practice by solving most interview questions.
| Short | Medium | Long | |
|---|---|---|---|
| Read through the System design topics to get a broad understanding of how systems work | :+1: | :+1: | :+1: |
| Read through a few articles in the Company engineering blogs for the companies you are interviewing with | :+1: | :+1: | :+1: |
| Read through a few Real world architectures | :+1: | :+1: | :+1: |
| Review How to approach a system design interview question | :+1: | :+1: | :+1: |
| 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
- 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:
- Use back of the envelope calculations
- Powers of two table
- Latency numbers every programmer should know
Source(s) and further reading
Check out the following links to get a better idea of what to expect:
- How to ace a systems design interview
- The system design interview
- Intro to Architecture and Systems Design Interviews
- System design template
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 and search (or Facebook feed and 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)
Design the Twitter timeline and search (or Facebook feed and search)
Design a web crawler
Design Mint.com
Design the data structures for a social network
[View exercise and
