Cadence is an open-source durable execution engine that lets developers write fault-tolerant, long-running workflows as code. Workflows and activities are defined in languages such as Go and Java. Cadence persists the execution history, retries failed activities automatically and resumes workflows from the point of failure, without separate message queues. State can be stored in Cassandra, PostgreSQL or MySQL, with OpenSearch supported for search. Cadence is not a hosted service but software that you deploy yourself, for example with Docker or with Helm charts on Kubernetes.
Cadence originated at Uber, a US company, and is released under the Apache 2.0 licence. It is a CNCF project, and its copyright notice names "Cadence a Series of LF Projects, LLC", which points to neutral foundation governance rather than control by a single vendor. Because you run Cadence yourself, your own infrastructure determines where data resides: on European servers, execution history and workflow data stay in Europe. There is no vendor cloud service whose hosting location would need to be checked.