The workflow tracks the workflow execution and status in a DynamoDB table. When the workflow starts, an idempotency key is calculated based on the input event (customizable) and stored in the database as a semaphore together with a status of IN_PROGRESS.

If storing the key was successful, the workflow runs the actual workflow steps and records the result in the database with a status of SUCCESS (or FAILED in case of an error).

If acquiring the semaphore was not successful (i.e. the workflow successfully executed previously or another execution is running concurrently and thus the status is IN_PROGRESS) the workflow retrieves the idempotency record from the database. When the status is SUCCESS and there is a result the result is returned as output of the workflow. If the status is IN_PROGRESS the workflow continues to query the database every 10 seconds until the status changes to either SUCCESS and it continues as described above, or FAILED, in which case the workflow tries to acquire the semaphore again.