AMC: parallel workflow execution limit reached
At most 10 workflow executions per instance and 200 per account run in parallel via the API; further ones wait in the queue.
Symptom
New executions stay in the PENDING status instead of running.
Cause
The API allows 10 parallel executions at instance level and 200 at account level. At account level the number of queued executions is not limited. PENDING means, per the docs: not yet started, queued, waiting for data or waiting until a specified time.
Fix
- Wait until running or queued executions finish.
- Remove executions you no longer need from the queue with DELETE /workflowExecutions/{workflowExecutionId}.
- Bundle queries so fewer executions are needed at the same time.
The cause follows the Amazon documentation. Some of the fix steps are our own judgement and do not replace asking Amazon support.