Error: dynamodb validation error detected

“Validation error detected” means a request parameter failed validation. Read the full message, including the named field and constraint. DynamoDB will reject the same invalid request again, so fix the input rather than adding retries.

1. Compare the table’s KeySchema and AttributeDefinitions with the request. Include every required key attribute with the right type.
2. Check the client layer: low-level clients require typed AttributeValue objects, while document clients accept native values.
3. Validate expression syntax and bind every referenced name and value placeholder. Do not send empty expression strings.
4. Check empty sets, empty key values, invalid numbers, and the 400 KB resulting-item limit. Empty non-key strings are allowed.

A primary key already existing is not automatically a validation error. PutItem replaces that item unless a condition prevents it. Use attribute_not_exists for create-only writes and handle ConditionalCheckFailedException separately. Record the error code and sanitized parameter shape to make the failing input reproducible.

See attribute types and AWS documentation.