Media are blobs stored beside the repository: uploaded first into temporary storage, then referenced from a record by CID, type and size; unreferenced blobs are garbage collected; quotas are the host's, accepted types and sizes the schema's.

It explains why media behaves differently from records in sync and migration.

Images, video, audio: blobs. Parcels that live beside the repository, not inside it.

You upload a blob to your host first. It waits on a temporary shelf, not yet visible to anyone.

Then a record references it: the blob's CID, its type, and its size. Now the host keeps it, and serves it.

A blob nothing references is deleted after a while. Delete the last record that points at it, and the blob goes too.

Quotas are the host's call. Which types and sizes a record may carry is the schema's call, checked when the record is written.

Check yourself. When does a host start keeping an uploaded blob for good?