Payment Queue Visibility Timeouts and Concurrency Races

Backend/SDE Coding I recently interviewed for a Backend/SDE role. The coding problem leaned toward backend work and concurrency. The problem was to implement an in-memory payment queue providing submit, receive, and ack. Requirements: submit adds a message. receive gets the next message. After a message is received, other consumers cannot get it during the visibility timeout. ack deletes it. If t…

Shared by a candidate · reported Sep 2026. Interview formats change; use it as a guide, not a script.