Introduction to System Design.

Hey there, my internet stranger friends! 👋

So we're starting this System Design Academy thing. I think, the best way to kick things off is by sharing something that happened to me a couple of years back.

I was preparing for this system design interview at this startup. Spent weeks watching YouTube videos, reading blogs, memorizing how to design Twitter, Instagram, all the classics. Before the call, I felt confident.

The interviewer asked me to design a messaging app. I started drawing the boxes and arrows I'd practiced. Database here, load balancer there. Then they asked: "What happens when your database in a region goes down?"

I froze.

That's when it hit me – I was treating system design like memorization instead of understanding what I was building.

What exactly is System Design?

You're planning a massive wedding for ~2000 people. You need to figure out the venue, catering, seating arrangements, parking, security, and what happens if it rains. You're essentially designing a "system" to handle this big event smoothly.

System design is pretty much the same thing, but for software.

It is an art. Art of designing large-scale software systems that handles millions of users, process lots of data, and still work when things go south.

Core challenges we solve

• Scalability - How do we handle growth from ~100 users to 100 M+ users?
• Reliability - What happens when servers crash? How do we ensure the system stays up?
• Performance - How do we keep response times fast and handle thousands of requests per second?
• Consistency - How do we keep data synchronized across multiple servers?

Let's take an example, building the next WhatsApp. Here's how system design thinking evolves:

Version 1:

• One server running in your hostel room
• One database (probably MySQL)
• Works for you and your 50 friends
• Crashes when everyone uses it during exam season

Version 2:

• Multiple servers
• Load balancer
• Database starts getting overwhelmed
• Works for like 10,000 users
• Still crashes during major cricket matches

Version 3:

• Servers in different regions
• Multiple databases with smart partitioning
• Caching layers everywhere
• Real-time message delivery system that actually works
• Handles millions of users
• Only crashes during World Cup finals (kind of acceptable)

So, Each version requires completely different system design decisions.

Everything you use daily runs on these principles. Your food delivery app, YouTube, banking apps – all built using system design concepts.

And from a career angle, companies pay really really well for engineers who understand this.

Hey, Don't worry if this feels overwhelming. System design is like learning to drive. It's always scary at first. Trust me, once you get the hang of it, you'll wonder how you ever lived without this knowledge.