Error: DynamoDB error 400

HTTP 400 is not a complete DynamoDB diagnosis. It can accompany invalid parameters, failed conditions, authentication or authorization problems, missing resources, and retryable throttling. Use the exception name and message to choose the fix.

• ValidationException: correct the named parameter, key type, expression, or data limit. Do not retry unchanged input.
• ConditionalCheckFailedException: the condition rejected the write. Recheck the business state rather than removing the guard.
• Credential or access errors: repair the session, signature, or permission for the specific API.
• ResourceNotFoundException: confirm the table or index and client environment.
• Throttling exceptions: inspect ThrottlingReasons and the affected resource, then use bounded backoff and address the limit.

Log the error code, HTTP status, and request ID rather than only “400.” SDK retry classifiers understand distinctions that a blanket “never retry 4xx” rule misses. Conversely, retrying every 400 can conceal a permanently invalid request.

See specific exception fixes and AWS documentation.