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System Design 101

Explain complex systems using visuals and simple terms.

Whether you’re preparing for a System Design Interview or you simply want to understand how systems work beneath the surface, we hope this repository will help you achieve that.

Table of Contents

• API and Web Development
  • Short/long polling, SSE, WebSocket
  • Load Balancer Realistic Use Cases
  • 5 HTTP Status Codes That Should Never Have Been Created
  • How does gRPC work?
  • How NAT Enabled the Internet
  • Important Things About HTTP Headers
  • Internet Traffic Routing Policies
  • How Browsers Render Web Pages
  • What makes HTTP2 faster than HTTP1?
  • What is CSS (Cascading Style Sheets)?
  • Key Use Cases for Load Balancers
  • 18 Common Ports Worth Knowing
  • What are the differences between WAN, LAN, PAN and MAN?
  • How does Javascript Work?
  • 8 Tips for Efficient API Design
  • Reverse Proxy vs. API Gateway vs. Load Balancer
  • How does REST API work?
  • Load Balancer vs. API Gateway
  • How GraphQL Works at LinkedIn
  • GraphQL Adoption Patterns
  • A cheat sheet for API designs
  • API Gateway 101
  • Top 3 API Gateway Use Cases
  • What do version numbers mean?
  • Do you know all the components of a URL?
  • Unicast vs Broadcast vs Multicast vs Anycast
  • 10 Essential Components of a Production Web Application
  • URL, URI, URN - Differences Explained
  • API vs SDK
  • A Cheatsheet to Build Secure APIs
  • HTTP Status Codes You Should Know
  • SOAP vs REST vs GraphQL vs RPC
  • A Cheatsheet on Comparing API Architectural Styles
  • Top 9 HTTP Request Methods
  • What is a Load Balancer?
  • Proxy vs Reverse Proxy
  • HTTP/1 -> HTTP/2 -> HTTP/3
  • Polling vs Webhooks
  • How do we Perform Pagination in API Design?
  • How to Design Effective and Safe APIs
  • How to Design Secure Web API Access
  • What Does an API Gateway Do?
  • What is gRPC?
  • Top 12 Tips for API Security
  • Explaining 9 Types of API Testing
  • REST API vs. GraphQL
  • What is GraphQL?
  • REST API Cheatsheet
  • The Ultimate API Learning Roadmap
  • The Evolving Landscape of API Protocols in 2023
• Real World Case Studies
  • 100X Postgres Scaling at Figma
  • API of APIs - App Integrations
  • The one-line change that reduced clone times by 99% at Pinterest
  • Is Telegram Secure?
  • Fixing Bugs Automatically at Meta Scale
  • How Levelsfyi Scaled to Millions of Users with Google Sheets
  • McDonald’s Event-Driven Architecture
  • Uber Tech Stack - CI/CD
  • How to Design Stack Overflow
  • Twitter 1.0 Tech Stack
  • How does Twitter recommend “For You” Timeline in 1.5 seconds?
  • How YouTube Handles Massive Video Uploads
  • How Does a Typical Push Notification System Work?
  • 4 Ways Netflix Uses Caching
  • Netflix Tech Stack - Databases
  • 0 to 1.5 Billion Guests: Airbnb’s Architectural Evolution
  • How Netflix Scales Push Messaging
  • Netflix’s Overall Architecture
  • Netflix Tech Stack - CI/CD Pipeline
  • How TikTok Manages a 200K File Frontend MonoRepo
  • How Netflix Really Uses Java
  • Evolution of Airbnb’s Microservice Architecture
  • Reddit’s Core Architecture
  • 10 Principles for Building Resilient Payment Systems
  • What is the Journey of a Slack Message?
  • Top 9 Engineering Blogs
  • Uber Tech Stack
  • Evolution of the Netflix API Architecture
  • How Discord Stores Trillions of Messages
  • Twitter Architecture 2022 vs. 2012
  • Evolution of Uber’s API Layer
  • Netflix’s Tech Stack
• AI and Machine Learning
  • 5 Functions to Merge Data with Pandas
  • Key Data Terms
  • ChatGPT Timeline
  • DeepSeek 1-Pager
  • The Open Source AI Stack
  • What is an AI Agent?
  • Data Pipelines Overview
  • How does ChatGPT work?
• Database and Storage
  • Read Replica Pattern
  • Pessimistic vs Optimistic Locking
  • How to Upload a Large File to S3
  • Types of Message Queues
  • Smooth Data Migration with Avro
  • The Ultimate Kafka 101 You Cannot Miss
  • Database Isolation Levels
  • Top 6 Data Management Patterns
  • Why is Kafka Fast?
  • Explaining the 4 Most Commonly Used Types of Queues
  • Time Series DB (TSDB) in 20 Lines
  • Differences in Event Sourcing System Design
  • Erasure Coding
  • Delivery Semantics
  • Change Data Capture: Key to Leverage Real-time Data
  • Can Kafka Lose Messages?
  • Storage Systems Overview
  • Explain the Top 6 Use Cases of Object Stores
  • Top Eventual Consistency Patterns You Must Know
  • B-Tree vs. LSM-Tree
  • How to Decide Which Type of Database to Use
  • Cloud Database Cheat Sheet
  • Types of Memory
  • Understanding Database Types
  • Top 4 Data Sharding Algorithms Explained
  • Top 6 Database Models
  • SQL Statement Execution in Database
  • What is Serverless DB?
  • Why PostgreSQL is the Most Loved Database
  • Top 10 Most Popular Open-Source Databases
  • Is PostgreSQL Eating the Database World?
  • How to Choose the Right Database
  • iQIYI Database Selection Trees
  • 8 Data Structures That Power Your Databases
  • How to Implement Read Replica Pattern
  • A Crash Course on Database Sharding
  • IBM MQ -> RabbitMQ -> Kafka -> Pulsar: Message Queue Evolution
  • CAP Theorem: One of the Most Misunderstood Terms
  • Consistent Hashing Explained
  • Types of Databases
  • Key Concepts to Understand Database Sharding
  • Database Locks Explained
  • A Cheatsheet on Database Performance
  • What does ACID mean?
  • Top 5 Kafka Use Cases
  • Types of Memory and Storage
  • 7 Must-Know Strategies to Scale Your Database
• Technical Interviews
  • How do SQL Joins Work?
  • What Happens When You Type google.com Into a Browser?
  • What Happens When You Type a URL Into Your Browser?
  • How to Ace System Design Interviews
  • Recommended Materials for Technical Interviews
• Caching & Performance
  • What is ELK Stack and Why is it Popular?
  • Why are Content Delivery Networks (CDN) so Popular?
  • How Big Keys Impact Redis Persistence
  • A Beginner’s Guide to CDN
  • The Ultimate Redis 101
  • Cache Systems Every Developer Should Know
  • Top 5 Strategies to Reduce Latency
  • Top 5 Caching Strategies
  • Things to Consider When Using Cache
  • Cache Eviction Policies
  • Memcached vs Redis
  • Low Latency Stock Exchange
  • Cache Miss Attack
  • Top 8 Cache Eviction Strategies
  • How Can Cache Systems Go Wrong?
  • Top 6 Elasticsearch Use Cases
  • How Does CDN Work?
  • How Redis Architecture Evolved
  • How Does Redis Persist Data?
  • How can Redis be used?
  • Why is Redis so Fast?
  • How to Learn Elasticsearch
  • What is CDN (Content Delivery Network)?
  • Frontend Performance Optimization
  • Which Latency Numbers Should You Know?
  • Top Caching Strategies
  • Top 9 Website Performance Metrics You Cannot Ignore
  • Top 5 Common Ways to Improve API Performance
  • Learn Cache
• Payment and Fintech
  • E-commerce Workflow
  • Digital Wallets: Banks vs. Blockchain
  • What is a Stop-Loss Order and How Does it Work?
  • What is Web 3.0? Why doesn’t it have ads?
  • SWIFT Payment Messaging System
  • 4 Ways of QR Code Payment
  • Handling Hotspot Accounts
  • Reconciliation in Payment
  • Unified Payments Interface (UPI)
  • How Scan to Pay Works
  • Money Movement
  • Payment System
  • How to Learn Payments
  • The Payments Ecosystem
  • Foreign Exchange Payments
  • How to Avoid Double Payment
  • How do Apple Pay and Google Pay work?
  • How VISA Works When Swiping a Credit Card
  • How ACH Payment Works
  • How does Visa make money?
• Software Architecture
  • Inter-Process Communication on Linux
  • Orchestration vs. Choreography in Microservices
  • UML Class Diagrams Cheatsheet
  • Amazon Prime Video Monitoring Service
  • Is Microservice Architecture the Silver Bullet?
  • Database Middleware
  • 9 Best Practices for Developing Microservices
  • Design Patterns Cheat Sheet
  • Key Terms in Domain-Driven Design
  • 8 Key OOP Concepts Every Developer Should Know
  • 18 Key Design Patterns Every Developer Should Know
  • 10 System Design Tradeoffs You Cannot Ignore
  • 9 Essential Components of a Production Microservice Application
  • 9 Best Practices for Building Microservices
  • 8 Key Concepts in Domain-Driven Design
  • 8 Common System Design Problems and Solutions
  • 6 Software Architectural Patterns You Must Know
  • How To Release A Mobile App
  • How Do Computer Programs Run?
  • Linux Boot Process Explained
  • MVC, MVP, MVVM, VIPER Patterns
  • The Ultimate Software Architect Knowledge Map
  • Typical Microservice Architecture
  • Top 5 Software Architectural Patterns
• DevTools & Productivity
  • Git Commands Cheat Sheet
  • How does Git Work?
  • JSON Crack: Visualize JSON Files
  • Git vs GitHub
  • Git Merge vs. Git Rebase
  • 30 Useful AI Apps That Can Help You in 2025
  • Diagram as Code
  • Top 9 Causes of 100% CPU Usage
  • Top 6 Tools to Turn Code into Beautiful Diagrams
  • Tools for Shipping Code to Production
  • Making Sense of Search Engine Optimization
  • Most Used Linux Commands Map
  • Linux File Permissions Illustrated
  • 5 Important Components of Linux
  • 15 Open-Source Projects That Changed the World
  • 20 Popular Open Source Projects Started by Big Companies
  • Linux File System Explained
  • Life is Short, Use Dev Tools
  • How Git Works
  • How do Companies Ship Code to Production?
• Software Development
  • Top 6 Most Commonly Used Server Types
  • How does Garbage Collection work?
  • A Roadmap for Full-Stack Development
  • What Are the Greenest Programming Languages?
  • Java Collection Hierarchy
  • Running C, C++, or Rust in a Web Browser
  • Top 8 C++ Use Cases
  • Top 6 Multithreading Design Patterns You Must Know
  • Data Transmission Between Applications
  • Blocking vs Non-Blocking Queue
  • Big Endian vs Little Endian
  • How to Avoid Crawling Duplicate URLs at Google Scale?
  • 10 Books for Software Developers
  • Top 8 Standards Every Developer Should Know
  • How Do C++, Java, Python Work?
  • 10 Key Data Structures We Use Every Day
  • A Brief History of Programming Languages
  • Top 6 Load Balancing Algorithms
  • The Fundamental Pillars of Object-Oriented Programming
  • Top 8 Programming Paradigms
  • Algorithms for System Design Interviews
  • Imperative vs Functional vs Object-oriented Programming
  • Explaining 9 Types of API Testing
  • The 9 Algorithms That Dominate Our World
  • Concurrency vs Parallelism
  • Linux Boot Process Explained
  • 11 Steps to Go From Junior to Senior Developer
  • 10 Good Coding Principles to Improve Code Quality
• Cloud & Distributed Systems
  • How AWS Lambda Works Behind the Scenes
  • 8 Must-Know Scalability Strategies
  • System Design Cheat Sheet
  • Cloud Disaster Recovery Strategies
  • Vertical vs Horizontal Partitioning
  • Top 9 Architectural Patterns for Data and Communication Flow
  • Top 6 Cases to Apply Idempotency
  • Top 5 Trade-offs in System Designs
  • How to Detect Node Failures in Distributed Systems
  • Why Meta, Google, and Amazon Stop Using Leap Seconds
  • The Fantastic Four of System Design
  • What makes AWS Lambda so fast?
  • Scaling Websites for Millions of Users
  • Resiliency Patterns
  • 25 Papers That Completely Transformed the Computer World
  • A Crash Course on Architectural Scalability
  • Must Know System Design Building Blocks
  • Monorepo vs. Microrepo: Which is Best?
  • How to Handle Web Request Errors
  • A Cheat Sheet for Designing Fault-Tolerant Systems
  • Typical AWS Network Architecture
  • Unique ID Generator
  • Amazon’s Build System: Brazil
  • Infrastructure as Code Landscape Cheatsheet
  • How do we manage configurations in a system?
  • How do we incorporate Event Sourcing into systems?
  • The 12-Factor App
  • Explaining 5 Unique ID Generators
  • Retry Strategies for System Failures
  • Cloud Monitoring Cheat Sheet
  • Why Use a Distributed Lock?
  • Top 6 Cloud Messaging Patterns
  • Most Important AWS Services to Learn
  • How to Transform a System to be Cloud Native
  • Hidden Costs of the Cloud
  • 2 Decades of Cloud Evolution
  • Cloud Cost Reduction Techniques
  • Top 7 Most-Used Distributed System Patterns
  • Cloud Load Balancer Cheat Sheet
  • AWS Services Evolution
  • Azure Services Cheat Sheet
  • A cheat sheet for system designs
  • CAP, BASE, SOLID, KISS, What do these acronyms mean?
  • System Design Blueprint: The Ultimate Guide
  • How to Design for High Availability
  • What is Cloud Native?
  • Cloud Comparison Cheat Sheet
  • Big Data Pipeline Cheatsheet for AWS, Azure, and Google Cloud
  • AWS Services Cheat Sheet
• How it Works?
  • How do AirTags work?
  • How is Email Delivered?
  • Design Gmail
  • How Google/Apple Maps Blur License Plates and Faces
  • Quadtree
  • Build a Simple Chat Application with Redis
  • Live Streaming Explained
  • How to Design a System for Internationalization
  • How to Design Google Docs
  • Payment System
  • Experiment Platform Architecture
  • Design Google Maps
  • Designing a Chat Application
  • Design Stock Exchange
  • How are Notifications Pushed to Our Phones or PCs?
  • What Happens When You Upload a File to Amazon S3?
  • Proximity Service
  • How Do Search Engines Work?
• DevOps and CI/CD
  • Top 10 Kubernetes Design Patterns
  • Some DevOps Books I Find Enlightening
  • Paradigm Shift: Developer to Tester Ratio
  • Push vs Pull in Metrics Collection Systems
  • Choose the Right Database for Metric Collection
  • Top 4 Kubernetes Service Types
  • Cloud Native Anti-Patterns
  • Kubernetes Tools Stack Wheel
  • Kubernetes Tools Ecosystem
  • Kubernetes Periodic Table
  • 9 Docker Best Practices You Must Know
  • Netflix Tech Stack - CI/CD Pipeline
  • Top 8 Must-Know Docker Concepts
  • CI/CD Simplified Visual Guide
  • Top 5 Most-Used Deployment Strategies
  • Kubernetes Command Cheatsheet
  • Kubernetes Deployment Strategies
  • How does Terraform turn Code into Cloud?
  • DevOps vs. SRE vs. Platform Engineering
  • Deployment Strategies
  • Logging, Tracing, and Metrics
  • Log Parsing Cheat Sheet
  • DevOps vs NoOps: What’s the Difference?
  • Why is Nginx so Popular?
  • What is Kubernetes (k8s)?
  • How does Docker work?
  • CI/CD Pipeline Explained in Simple Terms
• Security
  • What is DevSecOps?
  • Encoding vs Encryption vs Tokenization
  • Storing Passwords Safely: A Comprehensive Guide
  • Designing a Permission System
  • How Password Managers Work
  • Is PassKey Shaping a Passwordless Future?
  • Firewall Explained to Kids and Adults
  • Cookies vs Sessions
  • HTTP Cookies Explained With a Simple Diagram
  • Token, Cookie, Session
  • Sessions, Tokens, JWT, SSO, and OAuth Explained
  • How to Design a Secure System
  • Top 6 Firewall Use Cases
  • Top 4 Authentication Mechanisms
  • How Digital Signatures Work
  • How do we manage sensitive data in a system?
  • HTTPS, SSL Handshake, and Data Encryption Explained
  • Symmetric vs Asymmetric Encryption
  • Session-based Authentication vs. JWT
  • JWT 101: Key to Stateless Authentication
  • Is HTTPS Safe?
  • Cybersecurity 101
  • Cookies vs Sessions vs JWT vs PASETO
  • How does SSH work?
  • How Does a VPN Work?
  • How Google Authenticator Works
  • Types of VPNs
  • What is a Cookie?
  • OAuth 2.0 Flows
  • Top Network Security Cheatsheet
  • What is SSO (Single Sign-On)?
  • How does HTTPS work?
  • Session, Cookie, JWT, Token, SSO, and OAuth 2.0 Explained
  • Explaining JSON Web Token (JWT) to a 10 Year Old Kid
  • OAuth 2.0 Explained With Simple Terms
• Computer Fundamentals
  • Paging vs Segmentation
  • IPv4 vs. IPv6: Differences
  • Top 4 Most Popular Use Cases for UDP
  • How Does the Domain Name System (DNS) Lookup Work?
  • DNS Record Types You Should Know
  • TCP vs UDP for Online Gaming
  • What is a Deadlock?
  • Process vs Thread: Key Differences
  • OSI Model Explained
  • Visualizing a SQL Query
  • Explaining 8 Popular Network Protocols in 1 Diagram
  • What is the Best Way to Learn SQL?

License

This work is licensed under CC BY-NC-ND 4.0