Question: Can DynamoDB store blob data?

Answer

Yes. DynamoDB can store blob data in Binary attributes, but the entire item must fit within 400 KB. A blob cannot use the full allowance if the item also contains keys, attribute names and metadata.

Binary values suit small payloads that must be read or updated with the rest of an item. Use the SDK's binary representation, such as a byte array or Node.js Buffer. The low-level API transports binary as base64, but its item-size limit is calculated from the decoded bytes, not the base64 transport representation.

For larger objects, store the bytes in S3 and put the bucket and object key in DynamoDB. This separates large-file storage and delivery from indexed metadata lookups. Compression or splitting data into multiple items is possible, but adds retrieval and update complexity; compression also makes the compressed fields unavailable to DynamoDB expressions.

There is no transaction spanning an S3 write and a DynamoDB write. Plan retries and cleanup for objects whose metadata write fails, and decide which operation owns deletion. Never assume deleting the table removes the objects.

Use the item-size calculator before choosing inline storage, and compare the image-storage pattern.

Source: AWS large-item guidance.