Drag boxes, press run, and watch your design fall over before production does.
A free simulator for distributed systems: real queues, cascading failures, and capacity limits checked against textbook queueing theory.
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Watch These Break Under Load
Cascading failures are counter-intuitive. In a simulator, you see the exact tick where queues spiral out of control.
The Retry Storm
A 3-second traffic spike leaves worker queues locked and dropping requests long after traffic returns to normal. Backed-up clients trigger aggressive timeouts and duplicate retries, quadrupling real load.
The Unprotected Cache Outage
When a cache node dies without circuit breakers or fallback stubs enabled, every single query stampedes the database tier simultaneously, instantly exhausting pool connections and crashing replicas.
Worker Pool Starvation
A handful of unindexed slow analytical queries hold worker threads for 450ms. With zero thread isolation, unrelated lightweight /healthz calls get blocked, leading Kubernetes to erroneously restart healthy pods.
Load Balancer Blindspots
A 5-second health check probe interval leaves a blind window. When Node C segfaults, the balancer sends exactly 1,200 incoming customer requests into a black hole before marking the backend node dead.
Start from 10 Real-World Topologies
Pre-calibrated parameter sets ready to fork, mutate, and run. Derived directly from production interview questions and high-scale architectures.
URL Shortener
20,000 req/s read path with high cache hit ratio, base62 counter generator, and persistent relational storage fallback.
Chat Service
Persistent stateful WebSockets, gateway session affinity, Redis Pub/Sub backplane, and Cassandra chat message store.
News Feed
Hybrid write-time fan-out for active users, async celery queue workers, and read-through timeline cache layers.
Video Streaming
Multi-tiered CDN edge caching, video segment packaging workers, dynamic playback manifest resolution.
File Storage & Sync
Direct-to-object presigned chunking, conflict resolution, block deduplication cache, and metadata index servers.
Payment System
Kafka event queues, Redis idempotency tokens, two-phase commit coordinators, and exponential merchant webhook retries.
API Rate Limiter
Distributed sliding log algorithms, Redis sorted set evaluators, and zero-roundtrip local token bucket caches.
Notification System
Priority-tiered RabbitMQ queues (SMS > Push > Email), rate throttling wrappers, and external vendor fallback circuits.
Web Crawler
Politeness delay governors, Bloom filter URL deduplication, distributed frontier queues, and raw document storage.
Ride Sharing Engine
Spatial H3 / Geohash indexing for millions of live driver pings, trip state machines, lock-free batch matching algorithms, and bidirectional ETA dispatch streams.
How We Know It Works
We do not guess queue dynamics. Every commit to the event engine is automatically checked against closed-form solutions from operations research and classical queueing theory.
Validates that mean wait times match Erlang-C formulas across utilization levels ρ from 0.05 to 0.95 within 0.8% statistical tolerance.
Tests queue overflow and blocking probabilities against Erlang-B and finite state balance equations under continuous Poisson arrival bursts.
Proves that the long-term average number of items in the simulated system strictly equals arrival rate multiplied by total dwell time.
Verifies queuing delay under general, non-exponential service distributions: lognormal payloads, bimodal network packets, and Pareto bursts.
SYSTEM LAB validates the discrete event engine and queueing mathematics, not your proprietary application code or kernel drivers. It simulates topology contention, bounded buffers, backpressure, and network delay. It does not compile your Rust or Java code.
Engineered for Technical Depth
Interview Candidates
Move past memorizing high-level block diagrams. Test actual throughput limits and prove to interviewers why a single Redis cluster will cap out at 80,000 requests per second.
- ✓ Realistic back-of-the-envelope checks
- ✓ Identify bottlenecks under examination
Learners & Researchers
Watch abstract equations from textbooks come to life. Observe Little’s Law and Erlang-B blocking dynamically as you slide arrival rate and worker concurrency dials.
- ✓ Visual discrete-event clock ticking
- ✓ Zero math abstraction barriers
Practicing Architects
Size production instances before signing the cloud bill. Simulate peak Black Friday load spikes and discover whether your worker thread pool will starve your load balancer.
- ✓ Capacity reservation planning
- ✓ Circuit-breaker threshold sizing
Frequently Asked Questions
Start stress testing your architecture today.
No accounts, no setup, no cloud credentials. Just mathematically verified queueing simulation in your browser.