System Design
Capacity, trade-offs, and the diagrams that get you past the 'design Instagram' round — taught as decisions, not decorations.
Mastery unlocks after a 90% Quiz score
Real-world analogy
System design is city planning. You don't start with the opera house. You start with water, roads, and how many people show up at 6pm.
◎ Why it matters in production
Every 'it worked in staging' outage is a capacity or consistency story. This track trains you to name the trade-off before the interviewer asks for it.
Fundamental concepts you will master
Back-of-envelope
QPS, storage, bandwidth. A design without numbers is a moodboard.
The CAP you actually get
Latency vs consistency vs availability — pick two, then pick again at each layer.
Cache as a liability
Hit rate, stampede, invalidation. Cache is fast until it is wrong.
Queues as shock absorbers
Produce, consume, retry, dead-letter. The difference between a spike and an outage.
Step-by-step curriculum
The interview loop
Clarify, estimate, sketch, dive, trade-off. A repeatable 45-minute structure.
Building blocks
Load balancers, stores, caches, CDNs, queues — what each one actually buys you.
Data at scale
Sharding, replication, consistent hashing, and hot keys.
Classic prompts
URL shortener, news feed, chat, rate limiter — patterns you can reuse.
Failure
Idempotency, retries, backpressure, and the blast radius of a bad deploy.
Ready to see it in action?
Build your own path, step through operations, and watch mastery unlock after 90%.
Pointer Phantom
Direct Byte Access
+1,250 XP → Cache Ghost