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Learn how to design large-scale systems.

Prep for the system design interview.

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.

This is a continually updated, open source project.

Contributions are welcome!

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

The provided Anki flashcard decks use spaced repetition to help you retain key system design concepts.

• System design deck
• System design exercises deck
• Object oriented design exercises deck

Great for use while on-the-go.

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:

• Coding deck

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.

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
  • Availability in numbers
• 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
  • Relational database management system (RDBMS)
    • Master-slave replication
    • Master-master 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
  • Additional system design interview questions
  • Real world architectures
  • Company architectures
  • Company engineering blogs
• Under development
• Credits
• Contact info
• License

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.