Double booking

  • Fix
  • Quorum 18

Difficulty 3 of 5

Two transactions scan the same empty booking range, then each inserts a different row for slot 9. Prevent a phantom read and keep at most one committed booking in that range.

0:00. Two bookings hold slot 9. Graph: bookings in the range step from 0 to 2.

Play level

SQLUsers100 req/sPostgres1 vCPU · 1 GB
SQLUsers100 req/sPostgres1 vCPU · 1 GB
The board at the start of the level
An order and its event commit togetherTap to turn the outbox on or off

Outbox · 10 orders · 10 events · 0 lost

Goals and limits

Data mismatches
none
Phantom reads
none
Monthly cost
under 20 USD/mo
Edit limit
2
Traffic
100 req/s

Concepts

How players did

Player results load from the server.

All levels