What you'll be able to design by the end
Before the work begins, the payoff. By the last module you'll design eight marquee systems end-to-end, and, far more valuable, run one repeatable method on any "design X" you're handed.
Not "I've heard of it." "I can design it."
There's a gap between recognising a system's name and being able to build it on a whiteboard from a blank start: requirements, numbers, APIs, data model, architecture, scaling, failure. This course closes that gap on the systems people actually get asked about.
Each one hangs on a signature hard part. Learn those eight hard parts and you've seen most of what real systems throw at you.
Systems you'll build end-to-end
- Twitter / X home timeline The fan-out problem: push vs pull, and how celebrities break the naive design.
- WhatsApp Real-time messaging: delivery receipts, ordering, presence, offline queues.
- Stripe Payments you can't get wrong twice: idempotency keys, exactly-once, ledgers.
- Uber Match riders to drivers on a moving map: geospatial indexing at scale.
Four down. Each teaches one hard part you'll reuse everywhere else.
And the other four
- YouTube Serving video to the planet: transcode pipelines and CDN edge delivery.
- Dropbox Sync huge files cheaply: chunking, content-addressing, dedup, delta sync.
- Google Search Answer in milliseconds over billions of docs: inverted index, scatter-gather.
- Ticketmaster Ten thousand people, one seat: contention, holds, no double-booking.
Eight systems, eight signature hard parts: fan-out, messaging, idempotency, geospatial, CDN, dedup, indexing, contention.
The goal isn't to memorise these eight
If all you leave with is eight cached solutions, you'll freeze the first time someone asks for a ninth. The eight are vehicles. What you're really extracting is the method that produced them, the one you run when there's no cached answer.
- Memorise the answers Works right up until the question changes. Then you're stuck.
- Own the method Walk into any "design X" and run the same seven steps, on anything.
Seven steps you run on every design
Step 1Requirements & scopewhat it must do, and what you're refusing to build
Step 2Capacity estimateback-of-envelope QPS, storage, bandwidth
Step 3API contractthe handful of endpoints everything hangs off
Step 4Data model & storeswhat you store, and which store per data type
Step 5High-level architecturethe boxes and arrows that satisfy 1 to 4
Step 6Scale the bottlenecksfind the pressure point, then cache, shard, queue
Step 7Failure & operabilitywhat breaks, how you'd know, how it degrades
The method carries you into rooms you can't rehearse
- Nobody can memorise every possible "design X." But the same seven steps run on all of them. Master the method and an unfamiliar prompt stops being scary, it's just the framework again, with new numbers and a new signature hard part.
And at every step you'll be making the calls lesson 0.3 talked about: naming the trade-off, picking a position, defending it. The eight systems teach the hard parts; the framework gives you a place to put every decision, out loud, in order.
Eight systems to prove it, one method to repeat it, trade-offs you can defend
Eight marquee systems, end-to-end. Twitter, WhatsApp, Stripe, Uber, YouTube, Dropbox, Google Search, Ticketmaster, each a signature hard part.
One seven-step framework. Requirements, capacity, API, data, architecture, scale, failure, run on every design.
The real skill is transfer. Not the eight answers, the method that lets you handle a ninth you've never seen.
You've finished Start Here. Next, Module 1, lesson 1.1 · Why trade-offs are the whole game, where the six axes get mapped for real.