Explain ACID and transactions
Company: xAI
Role: Software Engineer
Category: System Design
Difficulty: medium
Interview Round: Technical Screen
What are the ACID properties of transactions? Define atomicity, consistency, isolation, and durability; explain how systems enforce them using logging, locking, MVCC, and write-ahead logging; discuss isolation levels and common anomalies; provide a concrete example transaction demonstrating ACID.
Overview: This question evaluates understanding of ACID transactional properties and the mechanisms that enforce them—including logging (undo/redo), locking, MVCC, and write-ahead logging—along with knowledge of SQL isolation levels and common transactional anomalies.