Breakscale

Breakscale is a system design simulator for learning how distributed systems behave under load. Users place components on a canvas, connect them into a topology, and increase traffic while observing latency percentiles, queue depth, circuit breakers, goodput, and cascading failures.

Its engine is a deterministic discrete-event simulation in which requests move through the topology. Components have finite server slots, instance counts, FIFO queues, and queue limits; service times use a gamma distribution based on a mean and coefficient of variation; timed-out downstream work continues consuming capacity; and queues acknowledge requests while buffering messages for workers. The simulator measures p50, p95, and p99 latency from completed requests and includes controls for crashing nodes, slowing services, forcing errors, or cutting links. The project provides system components such as load balancers, caches, databases, queues, workers, rate limiters, circuit breakers, shards, autoscalers, and stream brokers, along with teaching scenarios and reconstructions of published architectures.

The simulation engine is separated from the React interface and can be driven from a script. The repository is built with React, TypeScript, and Vite, runs locally with Bun, and is licensed under MIT; its bundled Caveat font is separately licensed under the SIL Open Font License 1.1.