Explain Distributed Transaction Patterns.

Distributed transaction patterns are methods to coordinate multi-step operations across multiple services or databases so that all steps either succeed or fail together.

When to Use

Use these patterns in microservices or multi-database systems where one action (like placing an order) requires consistent updates across different services.

Example

An e-commerce checkout updates the order, inventory, and payment systems; a distributed transaction ensures either all succeed or all roll back.

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Why Is It Important

Without these patterns, partial failures can leave data inconsistent (e.g., money deducted but order not created). They maintain data integrity and user trust.

Interview Tips

Be ready to compare Two-Phase Commit (2PC) and the Saga pattern:

• 2PC ensures atomicity but is slower and harder to scale.
• Saga uses compensating transactions for eventual consistency.

Showing awareness of trade-offs impresses interviewers.

Trade-offs

• 2PC: Strong consistency but reduced availability and performance.
• Saga: Scalable and fault-tolerant but only eventually consistent.

Pitfalls

Common mistakes include:

• Treating distributed transactions like local ones.
• Ignoring the need for compensating steps in Saga.
• Overengineering when eventual consistency is “good enough.”