Internal TLS certificate expired
At 00:00:30 UTC, right after midnight, your service-to-service calls to the internal `inventory` API begin failing with `certificate has expired` / `tls: failed to verify certificate`. It's all-or-nothing for that one dependency — every call fails — and it started exactly at midnight. Other dependencies are fine. The inventory team made no deploy; nothing changed on either side in the last 12 hours. The inventory API's TLS cert was issued by your internal CA. Browsers hitting inventory's public edge (which uses a different, Let's Encrypt cert) work fine. Pages are flooding in for every service that calls inventory. Triage this and lay out the immediate fix and the prevention.
Stop the bleeding first (mitigate), then form hypotheses from real signals. Separate root cause from symptom, communicate status as you go, and close with what prevents a repeat.