Editor’s note: Porter turns the Journal today over to Porter & Co. analyst Jared Simons. Jared took the lead in compiling September’s Complete Investor recommendation – a 14-year-old lending platform that is shaking up both the credit card and the retail industries.

In 1968, a mid-level banker in Seattle named Dee Hock was handed a mess.

Bank of America had licensed its BankAmericard – the first credit card you could use anywhere – to other banks, and the whole thing was coming apart. A dozen rival banks had to agree on how to approve and settle each other's transactions, and none of them trusted the others to run it.

Hock's answer was a consortium. He designed a network owned by no single bank, in which every member had a right to participate but no shares to sell. The banks would compete ferociously for customers and cooperate completely on the plumbing. He called it a system for the exchange of value. In 1976 it was renamed Visa.

The credit card might be the most successful piece of financial architecture of the last century. It's why you can hand a piece of plastic to a pub owner in London and have a bank in Ohio pay for the pint. And it has a flaw Hock spent the rest of his life warning about: he built it for its members, and it was eventually sold to shareholders. Visa (V) went public in 2008. The consortium became a landlord, collecting a toll on every purchase, at roughly the same rate, forever.

Underneath that toll is a technical decision from Hock's era that almost nobody outside the industry knows about.

When Visa built the first electronic approval system in 1973, it had to work over the phone lines of the day, at a cash register, with a customer standing there waiting. So it was built around a time limit. To this day, the card networks give the store, the banks, and the network about two and a half seconds to agree on a transaction. If they can't, it fails.

Think about what that forced. For 50 years, every decision about whether you get credit at the register – how much, at what price – has had to fit inside two and a half seconds. There's no time to shop your purchase to other lenders. No time for the store to offer to cover your interest, or for the manufacturer to say it will eat the financing cost to make the sale. So the industry did the only thing it could: it decided everything in advance. Your credit limit and your interest rate were set months ago, by a bank that has never seen what you're buying. The two and a half seconds just check that you're still under the limit.