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Streak

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Current levelLv 1

Curious Beginner

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Scaling

One server isn't enough. What would you do?

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Today's mission

Your queue has 1M pending jobs. Fix the backlog.

Take on the challenge →

Level 1 · System Foundations

Clients, servers, latency, throughput, scaling.

Scaling

One server isn't enough. What would you do?

● Simulator

Back-of-the-Envelope Estimation

How many servers do you need? Guess — then prove it.

● Simulator

Level 2 · Core Building Blocks

Load balancing, caching, replication, rate limiting, hashing.

Rate Limiter

Your API is under attack. Good luck.

● Simulator

Caching

Your database is dying. Add a cache.

● Simulator

Consistent Hashing

You have 4 servers and 10,000 keys. Now add server #5.

● Simulator

Unique ID Generator

Mint 2 million IDs a second. No duplicates. Ever.

● Simulator

Load Balancing

Spread the work so no single server drowns.

● Simulator

Database Replication

Your database just died. Good luck.

● Simulator

Level 3 · Design Patterns

Sharding, queues, consistency, backpressure.

Message Queues

Your queue has a million pending jobs. Fix the backlog.

● Simulator

Database Sharding

One database can't hold it all. Split it.

● Simulator

CAP & Consistency

Pick two. Actually, pick your poison.

● Simulator

Key-Value Store

Two replicas just died. Keep reads and writes flowing.

● Simulator

Level 4 · Real Systems

URL shortener, chat, feeds, video, payments.

More lessons landing here soon.

Level 5 · Interview Mode

Timed, unguided system-design challenges.

Unlocked in the Interview Arena.