Error: DynamoDB type is not supported

“Type is not supported” commonly means an SDK serializer or mapper cannot convert a language-specific value to DynamoDB. The service supports String, Number, Binary, Boolean, NULL, List, Map, and String, Number, and Binary sets. Non-key attributes are not declared in a fixed table-wide schema.

• Python: use Decimal for fractional numbers, bytes for binary, and dictionaries or lists for document data. Convert datetime and custom classes explicitly.
• JavaScript: normalize Date and class instances to the intended string, number, or plain-object representation. Decide how to handle undefined rather than relying on an accidental serializer default.
• Java or .NET mappers: supply a converter for unsupported model types and verify the stored attribute type matches the converter.
• All clients: reject empty sets, non-finite numbers, and unsupported key types. Table and index keys use scalar String, Number, or Binary values.

Inspect the exception stack to locate the rejected value. Avoid serializing every custom object into a string without considering how it will be queried later. Keep low-level typed AttributeValues separate from document-client native values.

See supported attribute types and AWS documentation.