:any – type inferred from the Elixir value on dump and from the DynamoDB tag on load. Uses the Dynamo.Encodable protocol for structs and custom values. Use an explicit type when you can; :any cannot round-trip atoms, dates or decimals, and always loads numbers as integers/floats.

Inference rules on dump: binaries → S (never B – use Dynamo.Raw or :binary), integers/floats → N, booleans → BOOL, nil → NULL, lists → L, maps → M, MapSet → SS/NS by element type, structs → Dynamo.Encodable.