> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/donnemartin/system-design-primer/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction

> Learn how to design large-scale systems and prep for the system design interview

## Motivation

<Note>
  **Learn how to design large-scale systems and prep for the system design interview.**
</Note>

### 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.

<CardGroup cols={2}>
  <Card title="Study guide" icon="book" href="/study-guide">
    Suggested topics to review based on your interview timeline
  </Card>

  <Card title="Anki flashcards" icon="brain" href="/anki-flashcards">
    Spaced repetition flashcard decks for key concepts
  </Card>
</CardGroup>

## How to approach a system design interview question

<Tip>
  The system design interview is an **open-ended conversation**. You are expected to lead it.
</Tip>

You can use the following steps to guide the discussion. To help solidify this process, work through the system design interview questions 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

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

### 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

## Additional resources

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

* [How to ace a systems design interview](https://web.archive.org/web/20210505130322/https://www.palantir.com/2011/10/how-to-rock-a-systems-design-interview/)
* [The system design interview](http://www.hiredintech.com/system-design)
* [Intro to Architecture and Systems Design Interviews](https://www.youtube.com/watch?v=ZgdS0EUmn70)
* [System design template](https://leetcode.com/discuss/career/229177/My-System-Design-Template)