Stampede

  • Fix
  • Level 10 of 41
  • Cache

Difficulty 1 of 5

At 0:20, all readers request one expired key. The database cannot serve 5,000 duplicate fills each second. Stop the miss burst and keep p99 below 150 ms.

0:20. One hot key expired. Graph: database CPU jumps to its limit as 5,000 copies of one read arrive each second.

Play level

HTTP/2SQLUsers5,000 req/sRedis cache0.25 vCPU · 0.5 GBPostgres0.5 vCPU · 1 GB
HTTP/2SQLUsers5,000 req/sRedis cache0.25 vCPU · 0.5 GBPostgres0.5 vCPU · 1 GB
The board at the start of the level
Cache size and hit ratioDrag or use arrow keys to change the cache size

1,600 keys · hit 81% · mean 3.2 ms

Goals and limits

p99 latency
under 150 ms
Error rate
under 0.01%
CPU use
under 70%
Monthly cost
under 30 USD/mo
Parts you can add
Redis cache, Memory cache
Part limit
16
Edit limit
3
Traffic
5,000 req/s

Concepts

How players did

Player results load from the server.

All levels