Based on my research, this appears to be a potential issue with the concurrency limits API endpoint behavior. While I can confirm that the endpoint exists and should handle incrementing concurrency slots, I cannot find explicit documentation or acknowledged issues about the 200 status code being returned in failure scenarios. This behavior you're describing - where a 200 status is returned even when the increment operation fails - could be a bug that should be reported. The API should ideally return an appropriate error status code (like 422 or 409) when it fails to increment the slots. I would recommend: 1. Creating a new issue on the Prefect GitHub repository to report this behavior 2. In your issue, include: - The specific API endpoint you're calling (/v2/concurrency_limits/increment) - The request payload you're using - The response you're getting (including the 200 status code) - The expected behavior - How you've verified that the slots weren't actually incremented Would you be able to share more details about how you're verifying that the increment operation is failing? This would help in creating a more detailed bug report and understanding the exact circumstances where this occurs. Also, are you using any specific client library to make these API calls, or are you calling the REST API directly? This information would be helpful for troubleshooting the issue.