The worst kind of outage is one nobody notices. Your metrics are green. Your dashboards are fine. Your users are quietly getting a broken experience.
I've been burned by three silent outages in my career. Here's how I catch them now.
How silent outages happen
Frontend caching the error. Your API returned a 500. Your CDN cached it. Now all users get the cached error for 10 minutes, but your API health check passes because the CDN never re-asks.
Partial feature breakage. Login works. Checkout works. The search bar silently returns empty results. Your dashboards don't track 'zero-result searches' so you don't see anything wrong.
