Distributed Transactions Explained: 2 Phase Commit vs Saga Pattern

In summary, the most interesting aspect is the industry's deliberate shift from theoretically perfect but practically flawed Two-Phase Commit to the pragmatic, eventually consistent Saga pattern, recognizing that large-scale systems prioritize availability and resilience over strict atomicity.

• Single-database transactions offer atomicity and isolation but fail to scale under heavy load.
• Splitting data across services breaks atomicity, creating distributed transaction challenges.
• Two-Phase Commit (2PC) guarantees strong consistency but is a blocking protocol prone to deadlocks and bottlenecks.
• The Saga pattern is the industry standard, trading strong consistency for eventual consistency and non-blocking operations.
• Sagas rely on compensating actions (like refunds) rather than rollbacks, which are visible and inherently imperfect.
• Orchestration is generally preferred over choreography for complex flows due to centralized visibility and control.
• The dual-write problem requires solutions like the transactional outbox pattern to ensure reliable event publishing.
• Co-locating related data in a single database is always the optimal first step to avoid distributed transactions entirely.