Design distributed transactions protocol
Company: Google
Role: Software Engineer
Category: System Design
Difficulty: hard
Interview Round: Technical Screen
Design a distributed transactions protocol to coordinate updates across multiple services or databases. Compare two-phase commit, three-phase commit, and Saga patterns; specify message flows, failure handling, idempotency, timeouts, and exactly-once versus at-least-once guarantees.
Overview: This question evaluates a candidate's understanding of distributed transactions, coordination protocols, fault tolerance, consistency, and reliability across microservices and databases.