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Engineering playground

Backend ideas, made visible

Press the buttons and watch the system react. Each simulation is a few lines of real logic you can reason about.

Token bucket rate limiter

Capacity 5 tokens, refilled at 1/s. Each request takes one token; with none left the request gets HTTP 429.

5.0/5

    Load balancer

    Send traffic to three app servers. Round-robin rotates blindly; least-connections sends each request to the least busy server.

    • app-10 active · 0
    • app-20 active · 0
    • app-30 active · 0

    LRU cache

    A cache with room for 4 keys. Reading a key moves it to the front; when full, the least recently used key is evicted.

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    Pick a key. · hit rate 0% (0/0)