Introduction to System Design

Devops Part 7 DevOps Docs

Introduction to System Design

✍️ 1.1 What is System Design?

System Design is the process of defining the architecture, components, modules, interfaces, and data for a system to satisfy specified requirements.

Think about it like this:

  • Building a small script = No big design needed.
  • Building an Instagram scale app = You need a proper design to handle millions of users, images, videos, scaling, security, etc.

✅ System Design is about:

  • How your system will handle millions of users?
  • How will it stay reliable if servers crash?
  • How will it scale up and down depending on the load?
  • How will it recover from disasters?
  • How secure and optimized will it be?

✍️ 1.2 Why System Design is Important?

  • Scalability: Your app should handle 1 user → 1M users easily.
  • Reliability: Systems shouldn’t crash if 1 server fails.
  • Performance: Response time should be fast.
  • Maintainability: Easy to update, monitor, debug.
  • Security: Secure user data and system.

In real world, even if your code is perfect, if the system crashes under load, users leave 🚀

✍️ 1.3 Types of System Design

Type Focus Area
High-Level Design (HLD) Big picture (services, APIs, databases, scaling, caching)
Low-Level Design (LLD) Class diagrams, APIs signatures, algorithms, DB schema

In interviews or real projects:

  • HLD = Overview Diagram, Database Choices, API Gateway, etc.
  • LLD = How will one service behave internally? (Classes, Methods, Tables)

🚀 Mini Challenge for You:

(Optional but recommended for better learning!)

🧠 Question: Imagine you are building a basic chat app (like WhatsApp).

How would you start thinking about it from a system design point of view? (not code – just broad ideas)

🚀 System design thought process would look like this for a Chat App:

Layer Focus
Clients Mobile apps / Web clients connecting via APIs.
API Gateway + Load Balancer Manage traffic coming in (horizontal scaling, sticky sessions if needed).
Chat Servers Stateless services handling chat messages in real time.
Database Store user info, messages metadata. Relational DB (Postgres, MySQL) + NoSQL (MongoDB, DynamoDB) depending on need.
File Storage Images/videos stored in S3 (object storage) or any blob storage.
Message Queue (Optional) For reliability — Kafka, RabbitMQ to handle delivery guarantees.
Caching Redis/Memcached for fast message reads, online status etc.
Monitoring & Alerts Track server health, latency, failures using CloudWatch, Datadog, etc.

🧠 In short:

When you think system design, break it into these:

Clients → Load Balancer → Backend Services → Databases → Storage → Caching → Monitoring