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

# Welcome

> A step-by-step guide to mastering High Level Design and Low Level Design for SWE interviews

## What is this site?

This is a personal learning guide for mastering **System Design** — both High Level Design (HLD) and Low Level Design (LLD) — built for software engineers preparing for interviews.

Every page here represents something I've learned, summarized in a way that's easy to follow and revisit.

## How to use this guide

<Steps>
  <Step title="Start with Foundations">
    If you're new to system design, begin with the Foundations section. It covers the core mental models you'll need before anything else.
  </Step>

  <Step title="Move to HLD">
    Learn the building blocks of large-scale systems — databases, caches, load balancers, and how they fit together.
  </Step>

  <Step title="Then tackle LLD">
    Dive into object-oriented design, SOLID principles, and design patterns with real case studies.
  </Step>

  <Step title="Practice for interviews">
    Use the Interview Prep section to structure your thinking and practice end-to-end problems.
  </Step>
</Steps>

## What's covered

<Columns cols={2}>
  <Card title="Foundations" icon="book-open" href="/foundations/what-is-system-design">
    Core concepts and how to approach any system design problem.
  </Card>

  <Card title="High Level Design" icon="building" href="/hld/building-blocks">
    Scalability, databases, caches, queues, CDNs and more.
  </Card>

  <Card title="Low Level Design" icon="code" href="/lld/oop-principles">
    OOP, SOLID principles, and Gang of Four design patterns.
  </Card>

  <Card title="Interview Prep" icon="clipboard-check" href="/interview/structure">
    How to structure answers, avoid common mistakes, and practice.
  </Card>
</Columns>