"In a microservices architecture, how do you ensure data consistency across services when a single business operation spans multiple databases?"
Alibaba's e-commerce platform involves complex multi-service transactions — placing an order touches inventory, payment, logistics, and loyalty points. This question tests your understanding of distributed transaction patterns and your ability to choose the right consistency model for different business scenarios.
Explain why traditional two-phase commit (2PC) doesn't scale well in microservices and introduce alternatives.
Describe the TCC (Try-Confirm-Cancel) pattern and when it's appropriate — high-consistency scenarios like payment deduction.
Explain the Saga pattern for long-running business processes where eventual consistency is acceptable.
Mention Alibaba's open-source Seata framework as a practical implementation, and describe how it coordinates global transactions.
In Alibaba's ecosystem, I'd choose the consistency model based on business criticality. For the checkout flow — where inventory deduction, payment, and order creation must be atomic — I'd use TCC via Seata. The "Try" phase reserves inventory and freezes the payment amount; "Confirm" finalizes both; "Cancel" rolls back if any service fails. For less critical flows like awarding loyalty points or sending notifications, I'd use the Saga pattern with a message queue: the order service publishes an "OrderCreated" event to RocketMQ, and downstream services consume it idempotently. Each service stores its local transaction result and can be compensated if needed. I'd also implement an idempotency layer using unique business keys to handle message retries safely, and a reconciliation job that runs hourly to detect and fix any inconsistencies between services.
Show awareness of trade-offs: TCC has higher complexity but stronger consistency; Saga is simpler but only eventually consistent.
Mention idempotency — it's critical in distributed systems and interviewers look for it.
Reference Seata (developed by Alibaba) to show you know their ecosystem.
Seata is an open-source distributed transaction framework created by Alibaba. It supports AT, TCC, Saga, and XA modes, allowing teams to choose the right consistency level for each business scenario without building custom coordination logic.
When possible, redesign the system to avoid cross-service transactions — for example, by using domain-driven design to keep related data in a single service. Distributed transactions should be a last resort, not a default.
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