last_seen means "this user did something recently". The backfill walks every
historical record in the network, so stamping it there recorded when the
backfill ran, not when the user was active — for every user at once, on every
run. That destroys the only signal the column carries, and it is the one column
in users that nothing upstream can rebuild.
It is now written on the two paths that represent real activity: an interactive
login, and a live commit event on the firehose, which does mean the user just
wrote a record. The backfill still corrects handle, PDS endpoint and avatar,
which is why it re-resolves rather than trusting a cache; it just no longer
claims the user was present.
UpsertUser grows an options form rather than a fourth named variant, since the
avatar and last_seen decisions are independent and all four combinations occur.
Anyone computing MAU from this column should know it was unreliable for every
backfill run before this change.
Also corrects docs/HORIZONTAL_SCALING.md, which claimed oci_client and
registry_domain were local-only preferences. They are fields on
io.atcr.sailor.profile: settings writes them to the user's PDS and
ProcessSailorProfile refreshes the local cache. users is fully derived apart
from last_seen.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Neither is a correctness problem; both are round trips on hot paths for
timestamps nothing reads at that resolution.
UpdateUserLastSeen ran per Jetstream event for cached users, so once per indexed
record. DeviceStore.UpdateLastUsed ran per /auth/token call, so once per docker
push and pull including each layer's re-auth. Cheap against a local file, a
network round trip each against a remote primary, and the second sat on the
authentication path.
Both are now throttled to once per five minutes per subject. The MAU queries and
the admin views work in hours or days, so nothing loses meaning. The throttle
state is per-process and lost on restart, costing at most one extra write per
subject per boot; only the lease holder runs the consumer, so exactly one process
is doing the first of these at a time.
UpdateLastUsed stamps the throttle before writing rather than after, so a slow or
failing write cannot let every concurrent layer upload through to pile on more of
them.
Verified by disabling the throttle: 50 back-to-back calls then rewrite the
timestamp every time.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Evan JarrettandClaude Opus 5