Module 1

Foundations

What system design is, how to approach a design interview, and the numbers and vocabulary every later topic builds on.

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Module 01

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1.1 Read
What Is System Design?
System design is deciding how the parts of a software system fit together so it stays fast, reliable and affordable as it grows. Here is what that means and a step-by-step way to approach any design question.
Beginner 8 min
1.2 Read
Performance vs Scalability
A performance problem makes a system slow for one user; a scalability problem makes it slow only when many users arrive. Learn the difference, and how scaling up and scaling out fix each.
Beginner 6 min
1.3 Read
Latency vs Throughput
Latency is how long one request takes; throughput is how many requests finish per second. Learn why percentiles beat averages, how Little's Law links the two, and why tail latency matters at scale.
Beginner 7 min
1.4 Read
Back-of-the-Envelope Estimation
Quick, rough calculations of requests per second, storage and bandwidth tell you which parts of a design will be under pressure. Learn the handful of numbers and a method you can use in any interview.
Beginner 5 min
1.5 Read
Latency Numbers Every Engineer Should Know
How long common operations take, from reading memory to sending a packet across the world, and what those gaps mean for design: keep data in memory, avoid round trips, and send less over long distances.
Beginner 5 min