The Orchestration pattern coordinates a multi-step business process by having a central orchestrator explicitly direct each participating microservice, which is well suited to workflows with clear sequential dependencies.
Key Points: • A central orchestrator service owns the overall workflow logic and calls each participating service in the correct order. • It's a good fit when steps have a clear dependency order and the business wants centralized visibility into where a given transaction currently stands. • The orchestrator can implement compensating actions if any step fails partway through, rolling back previously completed steps. • Compared to choreography, orchestration makes it easier to monitor and modify the overall workflow since the logic lives in one place rather than being scattered across event listeners. • The trade-off is that the orchestrator becomes a central dependency — if it's down, workflow execution stops.
Example: In an online travel booking system, an orchestrator coordinates flight, hotel, and car rental bookings: it first calls the flight service to reserve a seat, then the hotel service to secure a room, and finally the car rental service, ensuring each step completes (or is compensated) before moving to the next.
Interview Tip: A concise interview answer is:
"A travel booking system is a classic example — an orchestrator directs the flight, hotel, and car rental services in sequence for each booking, keeping the whole multi-step process centrally coordinated and making it straightforward to add compensating actions if, say, the car rental step fails after the flight and hotel are already booked."