The most dangerous integration failure is the one that doesn't throw an error. A token expires, a webhook endpoint starts returning 5xx, an app gets uninstalled — and your inventory sync, order routing, or finance feed just… stops. Everything looks fine until days later when the numbers are wrong and customers are angry.
Don't rely on "no errors in my inbox" — silence is exactly the failure mode. Instead, actively probe each integration on a schedule: make a cheap authorized API call and confirm it succeeds, and track the timestamp of the last successful data update per feed. If a feed hasn't updated within its expected window, or an authorized call starts returning 401/403, that's your early warning — hours or days before it shows up as wrong stock or missed orders.
A 401 on a previously-working token is an unambiguous "your integration is down" signal. Alert on it the moment it happens.