A counter with no coordination

  • Build
  • Quorum 24

Difficulty 4 of 5

Fans like a post at 9,000/s in 3 regions. At 0:20 a cut separates the regions for 15 s. Every like must be accepted with p99 under 40 ms, and none may be lost when the cut ends. The copies are 90 ms and 160 ms apart. Budget: 40 USD/month.

Play level

HTTP/2Users9,000 req/sKey-value s…1 vCPU · 1 GB × 3
HTTP/2Users9,000 req/sKey-value s…1 vCPU · 1 GB × 3
The board at the start of the level
Read and write quorumsLeft and right arrows change R. Tap to change W.

W 3 + R 3 of 5 · every read sees the last write

Goals and limits

Lost writes
none
Availability
at least 99%
p99 latency
under 40 ms
CPU use
under 80%
Monthly cost
under 40 USD/mo
Traffic
9,000 req/s

Concepts

How players did

Player results load from the server.

All levels