The per-QSO API is the only correct way to send a SELECTION, and at the
pace it must be driven a 14k backlog costs the better part of an hour.
HamQTH's other endpoint takes a whole log as one file — and REPLACES
what is on the site with it: its documentation says plainly that partial
uploads do not exist. So it is offered as its own deliberate act behind
a confirmation, never as the batch path behind 'send these', where it
would delete every QSO the operator had not selected.
Scoped to the callsign this profile uploads as, so a database holding
two operators' contacts cannot push one into the other's log; tar.gz
above 12 MB because the ceiling is 20 and a six-figure log passes it as
text; and every QSO not already stamped is marked sent afterwards, in
bulk, so the backlog list agrees with reality.