Observed arrival · 2026-09-14

System Design 101

systemdesign101.online Observed source

Editorial interest 87/100 Selection signal · not a rating of the site

An interactive system-design playground that lets you model traffic, capacity, failures, latency, autoscaling, and infrastructure cost.

Landing page captured for the 2026-09-14 issue.

Field notes

The playground asks users to declare traffic routing, per-part capacity, replication, and autoscaling behavior rather than inferring those choices. It can run a spike timeline, expose the interval before new instances boot, and compare costs as drawn, sized for peak, or autoscaled. The library includes worked systems such as a URL shortener, rate limiter, and distributed key-value store, with scenarios for retry storms, lost regions, and cache failures.

Observed signals

Read the marks

Editorial observations of this landing page, not a rating.

○OpenPublic substance visible

✦PrettyNotable craft visible

●ProPolished or operationally mature

◎NicheUnusually specific use

ƒJavaScriptBrowser-side code central

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