Wirebox

Learn system design by breaking it.

A free course. You build Gatepass, a ticketing app for gigs, then flood it with traffic and fix whatever fails first.

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Fans12k req/sLimiterper IPLoad balancerleast connsAPI 1API 2API 3RediscachePostgresprimaryDOWNBACK429HIT 94%● all 3 servers healthy · p99 84 msapi-2 failed health check · traffic reroutedapi-2 passed 3 checks · back in rotation

Three servers share the load. Fail one and watch where its requests go.

modules
19
modules
lessons
89
lessons
product drills
15
product drills
of material, all free
16 h
of material, all free

Lessons you can poke

This one is from the caching module. Drag the sliders and watch the hit rate and database load move. No video to sit through: each idea is a small system you run yourself.

Open the full lesson

Interactive

Cache hit-rate explorer

Gatepass serves 20,000 page reads a second across 5,000 pages. Choose how many pages the cache holds and how skewed the traffic is.

100 pages · 800 KB
Typical

The classic power law most real traffic follows.

0%25%50%75%100%1101001k5ktop k pages (log scale)57% hits

Hit rate

57%

DB queries/s

8,592

limit 4,000

Avg page read

timeouts

Cache memory

800 KB

2% of pages

Database load215%

The misses alone are more than the database can answer. Queues build, requests time out, and the cache's hits can't save the page.

The curve is the share of all requests that land on the most popular k pages. Where your cache size meets it is your hit rate. The database only sees the misses.

Then design a whole product

Each drill is a product brief and a blank canvas. You write the API, model the data, wire the architecture, and a simulator load-tests it step by step until it holds.

All 15 drills

One app, from one server to many cities

Gatepass starts on a single server for one college fest. Every module opens with the next problem it hits as it grows, and ends with the design that fixes it.

  1. Part 1: Foundations

    Grow one app from a single server to thousands of requests a second.

    • What is system design?49m
    • Start with one server2h 6m
    • Caching1h 12m
    • When one server isn't enough1h
    • When one database isn't enough49m
    • Live updates40m
    • Background jobs48m
    • Rate limiting38m
    • Growing big40m
    • Putting it together41m

  2. Part 2: Distributed systems

    What changes when the system is many machines that fail independently.

    • Microservices39m
    • Problems in distributed systems40m
    • Replication in depth56m
    • Partitioning in depth38m
    • Messaging: queues, pub/sub and Kafka42m
    • Transactions across services31m
    • Events and streams40m
    • Availability and going global31m

  3. Part 3: Under the hood

    The algorithms inside big systems, as simulations you can break.

    • Classic algorithms in action1h 14m

Free, all of it

The people who most need this material are often the ones least able to pay for it: students, people switching careers, developers where a course subscription costs a week's pay. So there is no paywall, no trial and no upsell. Sign in only to sync progress between devices.

Questions

Do I need an account?
No. Your progress saves in this browser as you go. Sign in only if you want it synced across devices. Accounts also help us count how many people are learning, which keeps the project going.
What do I need to know before starting?
You should be able to read a little code and know roughly what an HTTP request is. We start from a single server and one database, and build every idea on top of the last one. No prior distributed systems experience needed.
How do the drills work?
Each drill gives you a product brief, say a chat app. You write its API, model its data and wire up an architecture on a canvas. Then a simulator load-tests your design, step by step, from a handful of users to tens of thousands of requests a second. When something breaks, you get a debrief explaining why, and you fix it.
Will this help with system design interviews?
It should. The drills follow the same loop interviewers look for: requirements, estimates, a high-level design, then deep dives into the parts that hurt. We just teach it for real systems first, so the interview is the easy part.
How long does the course take?
About 16 hours across 89 lessons in 19 modules, plus the drills. Most lessons take ten minutes or so. Go at whatever pace suits you; your place is saved.
What is Gatepass?
The story that runs through the course: a ticketing app for gigs, comedy nights and college fests. It starts on one server for one fest and grows city by city. Every module begins with a problem Gatepass actually hits. Start with module 1.

Start with one server.

The first lesson takes 6 minutes. No sign-up, no card.

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