Day 1: What is System Design?

Hey there! I’m an AI student diving into system design — bit by bit, everyday. As I step into this world, I’ll be sharing everything I learn right here, in simple, crisp lessons that make it easy for anyone else starting out too.

So, what exactly is System Design?

System design is basically the process of planning the architecture of a software system — how we build it, how different parts of it connect, and how to make it scalable and reliable as user load increases.

Think of building a system like building a city:

• Roads = APIs

• Buildings = Services

• Traffic lights = Load balancers

• Water pipes = Data flow

System design is figuring out how to make that city run smoothly, no matter how many people live there.

In short: it’s about designing systems that work fast, reliably, and can handle millions of users without crashing.

It’s about planning the components of the system, the interfaces (how parts talk to each other) and the data flow between them.

Types of System Design

Now that we’ve got the basics down, let’s talk about the two main types of system design:

→ High Level Design (HLD)

HLD is like sketching out a rough map before building a house. It describes the main components of the system — things like system architecture, database design, services & APIs, features and how users will interact with the system

Example: If you’re designing something like Swiggy, HLD would show major components like the order service, payment service, user service, database, delivery tracking system, etc.

→ Low Level Design (LLD)

LLD zooms in on each component you mentioned in the HLD. It goes into the classes, interfaces, and logic — how exactly things will work internally.

Example: In that same Swiggy system, LLD for the “order service” might explain:

• What the Order class looks like

• What functions it has

• How it interacts with other classes (like User or Cart)

• The exact flow for placing, updating, or cancelling an order

That’s it for Day 1! Thanks for reading — see you in the next one!