A fingerprint comparison proves two archives agree about a key. Only
opening real ciphertext from the target proves the key in hand reads the
data, which is the question an operator actually has.
Every refusal happens before the first write: format, checksums, key
policy, then target inspection. A unique index that will not build aborts,
because the unique indexes here are tenant-isolation properties rather
than optimisations.
Collections are enumerated live rather than from a list, so a collection
added later is backed up with no code change. Documents are written as the
raw BSON the driver returned, so Decimal128, ObjectId, DateTime and binary
subtypes survive byte for byte.
Open extracts and verifies every member against the manifest before the
reader is usable, so a corrupt archive is refused before a restore writes
its first document rather than halfway through.
mrhid6