Dynamo DB isn’t even good at being a KV store. Almost every time we have to also back it with S3 because of size limitations.
did you use single table design?
and yeah you have to spend a lot of upfront time designing your data models
If you know your access patterns really well and they are non-relational, then you can design the best possible tables for dyanmoDB. In such a case DynamoDB works and scales amazingly. Ofc, you cannot do multi table relationships etc shoehorning a relational scheme onto DynamoDB does not work.