SAGA Pattern: Managing Distributed Transactions
Issue #63: System Design Interview Roadmap
When your microservices architecture grows beyond a few services, you'll inevitably face the challenge of maintaining data consistency across multiple databases. Traditional ACID transactions don't work across service boundaries, and distributed transactions using Two-Phase Commit (as we covered in Issue #62) often prove too rigid for modern cloud environments.
Enter the SAGA pattern—a choreographed dance of compensating actions that maintains eventual consistency without the brittleness of distributed locks. But here's what most engineers miss: SAGA isn't just about rolling back failed transactions. It's about designing your business processes to be inherently reversible.
The Hidden Complexity of Business Logic Reversibility
The most underestimated aspect of SAGA implementation isn't the technical orchestration—it's designing compensating actions that truly undo business operations. Consider a payment processing SAGA: reversing a credit card charge isn't simply subtracting the amount. You must handle partial refunds, interchange fees, currency fluctuations that occurred between the original transaction and compensation, and regulatory compliance for financial reversals.
This compensation complexity grows exponentially with business rule sophistication. A simple e-commerce order SAGA might involve:
• Inventory reservation (compensate: release reserved items)
• Payment processing (compensate: refund with fee considerations)
• Shipping allocation (compensate: cancel shipment, handle if already dispatched)
• Loyalty points award (compensate: deduct points, handle if already spent)
Each compensation isn't a simple inverse—it's a context-aware business operation that must handle the temporal gap between the original action and its reversal.
Choreography vs Orchestration: The Architectural Decision Matrix
📊 [IMAGE : SAGA Choreography vs Orchestration Comparison Diagram]