Separate NiFi's live canvas from the guarantees you actually depend on before you shop for a replacement, because the two get conflated. NiFi lets operators pause a single connection, inspect queued FlowFile attributes, replay content, and change a parameter while watching the result, a runtime debugging model few alternatives match. What most alternatives offer instead is engineering discipline: pipelines as code or config that you test, review, and release. Airflow and Prefect express work as Python DAGs and flows with scheduling and retries; Kestra keeps orchestration in declarative YAML versioned in Git; Mage builds pipelines block by block in a self-hosted notebook-style environment.
The closest structural match to NiFi's routing is Apache Camel, an integration framework with 350+ connectors and Enterprise Integration Patterns expressed as routes in Java, YAML, or XML. But even there, backpressure, provenance, and controller-service behavior do not translate one to one. Confirm how each candidate handles ordering, replay, offset or checkpoint tracking, and failure routing against your real flows, since processor coverage on paper rarely means identical semantics under load.
Treat the move as a rebuild with reference material rather than a conversion. NiFi flow definitions export cleanly and make excellent specifications, but almost no replacement executes them directly. Queued FlowFiles, provenance history, and repository contents do not migrate, so drain queues, re-enter secrets in the new store, then run old and new in parallel and compare record counts before cutting over one source at a time. Keeping schemas, secrets, and pipeline definitions in source control is what makes this migration, and any later one, tractable.