Real simulator
SimPy under the hood — M/M/c, M/G/1, Jackson networks. Every primitive validated to within 2% of the analytical math.
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Kendall
Distributed systems · simulated
Get Kendall on your phone
Kendall installs as a real app on Android and iOS — one-tap launch from your home screen. Copy this URL and open it on your phone to install.
Sketch your services on a canvas. Push real traffic through them. Watch a discrete-event simulator predict exactly where it’ll break — and what to do about it.
Same simulation, every browser. Real queueing math — M/M/c, M/G/1, Jackson networks — runs entirely on-device.
How it works
One concrete question — “will my system survive a 10× launch?” — answered in a few minutes, without provisioning anything.
Drag services onto a canvas. Wire them together. Set traffic patterns and SLOs.
React Flow · 200+ services
A discrete-event simulator runs the graph under load. Latency, queueing, and failure propagate the way they would in production.
SimPy · M/M/c · M/G/1 · Jackson
See exactly which service saturates and at what RPS. Try a fix, re-run, watch the verdict change.
Grounded LLM advice on request
Features
Kendall doesn’t draw your architecture — it runs it. Real services, real traffic, real numbers.
SimPy under the hood — M/M/c, M/G/1, Jackson networks. Every primitive validated to within 2% of the analytical math.
Per-region, per-instance AWS rates, refreshed weekly. Cross-validated against the official calculator on every release.
AZ outages, dependency timeouts, retry storms. Watch how cascades propagate and which mitigations hold.
Run up to five architectures in parallel. Diff latency, cost, and failure modes side by side.
AWS catalog ships first. GCP, Azure, and on-prem plug into the same engine without changes to the math.
Every LLM suggestion cites simulator numbers and is re-simulated before it surfaces. No vibes.
Who it’s for
Whether you’re scaling a startup, taking the course, or running it — Kendall meets you where you are.
Engineering teams
Compare three scaling strategies in an afternoon. Forecast cloud spend before you scale. Find bottlenecks before users do.
See the templatesStudents
Drag real architectures onto a canvas, push real load through them, and learn queueing theory by experimenting — not by memorizing.
Start learningEducators
Assign real architectures, run live simulations in lecture, and show — with a number, not a story — exactly why the database saturates.
Browse the lessonsMethodology
The product is named for Kendall notation — the way every queue in the simulator is classified. Every claim cites the math that backs it.
Little's Law
1961
L = λW
Mean number of requests in a stable system equals arrival rate times average wait. Asserted on every build.
Stability
1953
ρ < 1
Any infinite-buffer queue is stable only if arrival rate stays below service rate. Cross 1 and the queue grows unbounded.
Erlang C
1917
C(c, ρ)
Probability that an arriving request must wait in an M/M/c queue. Validated to within 2% of the closed form.
Pricing
We charge for cloud features once Phase 2 ships. Everything that runs in your browser stays free under Apache 2.0.
For individuals, students, educators.
For engineers who simulate often.
For companies scaling deliberately.
FAQ
Short answers. If something isn’t here, the designer is the fastest way to find the rest.
Yes. Every queueing primitive (M/M/c, M/G/1, Jackson networks, etc.) is validated on every CI build against its closed-form analytical formula to within 2% over 100,000-sample runs. If a sim result violates Little's Law, the build fails.
AWS now (200+ services). GCP and Azure catalogs land in Q1 and Q2 of 2027. The engine is provider-agnostic — catalogs plug in without modifying the simulator, so adding your own internal/on-prem service is straightforward.
Those tools draw your architecture. Kendall runs it. We forecast latency, throughput, and cost under load using actual queueing math — diagram tools just store rectangles and arrows.
No. Kendall runs entirely in your browser. Designs save locally to browser storage by default. Cloud sync (Pro) is opt-in.
On the Free plan, no. Everything runs locally in your browser, including the simulator. On the Pro plan, you opt-in to cloud sync if you want shareable links and version history.
Yes. The core simulator and AWS catalog are Apache 2.0, forever. Cloud features (sync, history, team workspaces) are the commercial layer.
Get started
Free during pre-alpha. Saves to your browser. No card, no signup, no agenda.