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fanout

Simulation run on this device. Scenario values are not sent anywhere — the engine is fully local.

system design simulation · free

Cache Stampede Lab

Expire a hot key under load and compare naive, lock, and jittered-TTL strategies.

How bad is expiry thundering-herd at this TTL?

Engine 1.0.0 · simulation
15000
s
1600
105000
1 0/1
Keys expiring / s (est.)
0.017×N
Stampede fan-out
1 (locked)
Origin QPS
4.0
Recompute cost
250 ms

Singleflight collapses stampede to one recompute.

TTL 60s, miss QPS 400, lock=on

Method

  • Deterministic local model of the mechanism — knobs recompute outputs instantly with no network.
  • Numbers are teaching approximations, not production capacity guarantees.

Sources

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