What is the key difference between orchestration and choreography?

The key difference between orchestration and choreography in the context of distributed systems and microservices lies in how interactions between services are managed.

Orchestration — centralized management of the process. There is one component (the orchestrator) that controls the sequence of calls and interactions between services. The orchestrator knows the logic of the process and directs services on when and what to do.

Choreography — decentralized interaction. Each service independently reacts to events and performs its actions without a central controller. The process is formed from a chain of reactions to events that are published and consumed by services.

Example:

• Orchestration: the order service calls the payment service, then the delivery service under the direction of the orchestrator.
• Choreography: the order service publishes an "Order Created" event, the payment service listens to this event and initiates payment, the delivery service listens to the "Payment Confirmed" event and starts delivery.

The choice depends on the requirements for control, scalability, and system complexity.