Watch latency spike, queues build, and requests get dropped — then switch strategies and see the tradeoff instantly.
When a system hits capacity, adding a queue feels like the responsible choice. Fewer errors. Calmer dashboards. But under sustained load, that queue is silently converting rejected requests into latency — and the longer it gets, the worse every user's experience becomes.
By the time you notice, your p95 is through the roof, timeouts are cascading, and the queue that was supposed to help is the reason your system feels broken. The overload was always there. The queue just hid it.
LoadLens makes this tradeoff visible instantly.
Powered by async-bulkhead-ts — the same admission control library used in production systems. Drag a slider, see the result immediately.
Fail-fast and bounded queue run simultaneously. Same parameters, different strategies. The difference is impossible to miss.
P95 latency, throughput, waiting requests, and rejections over time. Each one tells part of the overload story.
Step through overload behavior: from healthy → saturation → collapse. See exactly where things go wrong.
LoadLens surfaces the core tradeoff automatically: how many rejections the queue absorbed, and what it cost in latency.
Save scenarios locally. Export charts as PNG. Use LoadLens in architecture reviews, postmortems, and conference talks.
No. LoadLens builds intuition about overload behavior through simulation. It's an educational tool, not a replacement for observability, capacity planning, or load testing. Think of it as a whiteboard that runs real admission control logic.
LoadLens uses async-bulkhead-ts — a real concurrency-limiting library — under the hood. The simulation matches real bulkhead behavior for the parameters you configure. It uses deterministic arrivals and fixed work durations, which makes it ideal for building intuition. Real systems add variance, retries, and network effects that LoadLens intentionally omits for clarity.
The underlying concepts and simulation model are transparent, but the full product is not open source. LoadLens is designed to be used directly — no setup required.
No. LoadLens is a static web app. There is no backend, no analytics, no telemetry. Your simulations run entirely in your browser. Nothing leaves your machine.
Yes — LoadLens is a static web app. Share the URL with anyone on your team. No accounts, no seat limits.
That's intentionally out of scope. LoadLens is sharpest when it stays simple: a few controls, clear output, immediate insight. If you need production traffic simulation, you want a load testing tool. LoadLens helps you understand why your system behaves the way it does under load — before you run those tests.