Distributed Transactions & Saga

Two-phase commit gives strict atomicity across resources but holds locks across the network and needs a coordinator, so microservices prefer Saga plus Outbox with eventual consistency.

JTA/XA coordinates multiple resources atomically using two-phase commit (heavy and blocking), while @Modifying marks a Spring Data @Query as a DML statement that must run inside @Transactional and needs clearAutomatically to avoid stale entities.