The /download endpoint refers directly to store items. However, they can be GC’d in the meantime, in which case the HTTP handler fails gracelessly (HTTP 500 or so) as shown here:
--8<---------------cut here---------------start------------->8--- 2023-06-27 16:02:24 GET /download/718 2023-06-27 16:02:24 Uncaught exception in task: 2023-06-27 16:02:24 In fibers.scm: 2023-06-27 16:02:24 172:8 1 (_) 2023-06-27 16:02:24 In ice-9/boot-9.scm: 2023-06-27 16:02:24 1685:16 0 (raise-exception _ #:continuable? _) 2023-06-27 16:02:24 ice-9/boot-9.scm:1685:16: In procedure raise-exception: 2023-06-27 16:02:24 In procedure open-file: No such file or directory: "/gnu/store/bnsh1yk4l913af8swqi3x7xp1xsa8gq7-guix-binary.tar.xz" --8<---------------cut here---------------end--------------->8--- The solution IMO is to (1) register GC roots for these, (2) periodically remove old GC roots, and (3) return 404 when the file has vanished. Ludo’.