Symptoms
Checkout latency rises for everyone, payments logs card provider responded slowly, and payment_provider_status{provider="primary"} drops below 1 (0.5 means the provider's status page says degraded).
What we can do
We cannot fix the provider. We can route charges to the fallback provider with the payments.fallback_provider flag (rb-009). The fallback is slower than a healthy primary (about 150 to 250 ms) but much faster than a degraded one.
Decide
Switch to the fallback when the primary is degraded on its status page and provider latency explains the checkout latency. If the status page is green and latency is only slightly high, wait one alert window and check again.