Public Atom XML feed rendering currently active platform announcements from the shared announcements table. No Authorization header is required. The feed contains at most 50 entries, ordered descending by published_at (with a stable secondary id tiebreaker).

Active means published_at <= now() AND (expires_at IS NULL OR expires_at > now()). Empty active sets still return a valid Atom envelope with zero <entry> rows so aggregator-cache content hashes stay stable.

Cache-Control is public, max-age=300 — Cloudflare in front of the API will respect the hint. Announcements are not time-critical, so a 5-minute window is acceptable.

<updated> semantics: the feed-level <updated> is a best-effort change marker, not a linearizable version counter. It is the GREATEST of four signals — an edit to any announcement (including one that unpublishes a row by pushing published_at into the future), a scheduled announcement crossing into visibility, an active announcement crossing into expiry, or a hard delete — and it never exceeds the current time. Writes to different announcement rows take no shared lock, so two concurrent edits can commit in an order where the marker does not advance past a value a reader already observed even though a new change became visible in that window. Treat <updated> as a "poll again soon" hint, not a guarantee that an unchanged value means nothing changed since your last read. Per-entry <updated> is the later of that announcement's last edit and its published_at, clamped so it never exceeds the current time — a just-published scheduled announcement reads updated == published rather than updated-before-published, and a row whose last-edit timestamp is ahead of real time (clock skew, or accumulated strict-advance drift) reads the current time instead of that future value. Timestamps use full sub-second precision (RFC 3339 with fractional seconds) so edits within the same wall-clock second still render distinct values.