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:

• System design topic summaries
• Real world architectures
• Engineering blogs

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:

• 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

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.

• System design topics: start here
  • Step 1: Review the scalability video lecture
  • Step 2: Review the scalability article
  • Next steps
• Performance vs scalability
• Latency vs throughput
• Availability vs consistency
  • CAP theorem
    • CP - consistency and partition tolerance
    • AP - availability and partition tolerance
• Consistency patterns
  • Weak consistency
  • Eventual consistency
  • Strong consistency
• Availability patterns
  • Fail-over
  • Replication
• Domain name system
• Content delivery network
  • Push CDNs
  • Pull CDNs
• Load balancer
  • Active-passive
  • Active-active
  • Layer 4 load balancing
  • Layer 7 load balancing
  • Horizontal scaling
• Reverse proxy (web server)
  • Load balancer vs reverse proxy
• Application layer
  • Microservices
  • Service discovery
• Database
  • SQL
    • Relational database management system (RDBMS)
    • Scaling SQL
      • Master-slave replication
      • Federation
      • Sharding
      • Denormalization
      • SQL tuning
  • NoSQL
    • Key-value store
    • Document store
    • Wide column store
    • Graph Database
  • SQL or NoSQL
• Cache
  • Client caching
  • CDN caching
  • Web server caching
  • Database caching
  • Application caching
  • Caching at the database query level
  • Caching at the object level
  • When to update the cache
    • Cache-aside
    • Write-through
    • Write-behind (write-back)
    • Refresh-ahead
• Asynchronism
  • Message queues
  • Task queues
  • Back pressure
• Communication
  • Transmission control protocol (TCP)
  • User datagram protocol (UDP)
  • Remote procedure call (RPC)
  • Representational state transfer (REST)
• Security
• Appendix
  • Powers of two table
  • Latency numbers every programmer should know
• Under development
  • Distributed computing
  • Consistent hashing
  • Scatter gather
  • Contribute
• Credits
• Contact info
• License

Study guide

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

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