Mobile Cache Waterfall 2D: TTL & Stale-While-Revalidate

A mobile app's cache is rarely one thing — it is a small fast memory tier backed by a larger slower disk tier backed by the network, each with its own time-to-live. This simulator issues a live stream of requests against a Zipf-weighted set of items and lets each one fall through memory, then disk, then network exactly as a real client cache would, timing every hop. A stale-while-revalidate toggle shows the difference between silently refreshing an expired entry in the background versus forcing the user to wait on a synchronous network round-trip. A pannable/zoomable flow lane shows every request's path, live grids show exactly which keys occupy L1 and L2 and how close each is to expiry, and a rolling history strip tracks hit-rate and latency over time.