One bank route is failing. The average says it's fine.

transcript

This card route just fell from 92 to 60 percent approvals. And your dashboard barely moves.

Visa cards from issuer X. Acquirer P1 approves 92 percent. Acquirer P2, about 89. Close. Then, in five minutes, P1 drops to 60 percent. But only for issuer X.

Track one rate per processor? Every other issuer through P1 is fine. So P1's average barely moves. Or you panic and pull all of P1. Failures are local. So keep a rate per slice: method, network, issuer, processor. Now only issuer X's card traffic moves to P2.

A payment comes in. First, respect the merchant's rules. Some pin processors. Is this route down for this slice? Well below its baseline, with enough attempts. If not, send it to the best score. But here's the catch. Keep about 2 percent probing the down route.

Why? A route that failed once, and never gets traffic, is never measured again. And never trusted again.

One more rule. Only technical failures count against a route. A wrong OTP, or no funds? That's the customer's answer. Not the route's fault.

Failures are local. One issuer, through one acquirer. So route per slice, and keep probing the routes you've given up on.

Full breakdown in the lecture.