Cadence - Distributed, scalable, durable, and highly available orchestration engine to execute asynchronous long-running business logic in a scalable and resilient way

Cadence is a distributed, scalable, durable, and highly available orchestration engine we developed at Uber Engineering to execute asynchronous long-running business logic in a scalable and resilient way.

Business logic is modeled as workflows and activities. Workflows are the implementation of coordination logic. Its sole purpose is to orchestrate activity executions. Activities are the implementation of a particular task in the business logic. The workflow and activity implementation are hosted and executed in worker processes. These workers long-poll the Cadence server for tasks, execute the tasks by invoking either a workflow or activity implementation, and return the results of the task back to the Cadence server. Furthermore, the workers can be implemented as completely stateless services which in turn allows for unlimited horizontal scaling.