system-design-primer

simulation 05one shard takes the heat

The data is split across shards by key range, and most of the traffic wants keys that all live in the same range. One shard is pinned while its neighbours idle. Buying more shards divides the range further — it does not move the hot keys.

pass when
error rate ≤ 3% · p99 ≤ 320ms · spend ≤ $560

The simulation reads best on a wider screen — the topology is drawn left to right.

Ready to run.

served
0
dropped
0
error rate
0.0%
p99
0ms
in flight
0
build
spend$160 / $560

Capacity is never free. Passing under budget is the whole exercise.