How do you handle transactions across microservices?

Challenges: no single ACID database, network failures, partial failures. Patterns: Saga (sequence of local transactions with compensating actions - choreography or orchestration), Two-Phase Commit (2PC - coordinator ensures all-or-nothing, but blocking and slow), Event Sourcing + CQRS (events as truth, eventual consistency). Best practices: design for eventual consistency when possible, use idempotent operations, implement compensating transactions, track transaction state. Avoid distributed transactions when possible through service boundaries.