Promoted too soon

  • Fix
  • Quorum 02

Difficulty 2 of 5

At 0:40, the primary fails and stays down. Two followers apply writes after 100 ms; a third waits 500 ms. Keep every acknowledged write and serve all reads. Finish at least 99.5 percent of writes with write p99 below 250 ms. The group has four fixed copies.

0:40. The primary failed. Graph: 50 acknowledged writes are missing on the promoted follower.

Play level

SQLSQLUsers500 req/sUsers100 req/sPostgres1 vCPU · 2 GB × 4
SQLSQLUsers500 req/sUsers100 req/sPostgres1 vCPU · 2 GB × 4
The board at the start of the level
Copies and the write quorumDrag or use arrow keys to change the write quorum

Quorum 2 of 3 · commit 9.0 ms

Goals and limits

Lost writes
none
Availability (Reads)
at least 100%
Availability (Writes)
at least 99.5%
p99 latency (Writes)
under 250 ms
CPU use
under 80%
Monthly cost
under 60 USD/mo
Edit limit
3
Traffic
500 req/s

Concepts

How players did

Player results load from the server.

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