The requested resource is already being updated simultaneously by another API request. The last request will be rejected to avoid inconsistent state.
Possible Causes
The same API resource is being updated by multiple simultaneous API requests from different threads in a conflicting fashion.
Possible Solutions
Implement an operation retrier and repeat the failed API requests after an interval of time using, exponential backoff algorithm.
Serialize your API requests that modify the same resources, and wait until the original request completes and returns an API response, before sending any successive modifications.