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Square is built on relatively modern (eg this century) tech stack. Modern tech stack are inherently more fragile than the real legacy stuff. The Mainframe tech
by tpurves 3y ago
Square is built on relatively modern (eg this century) tech stack. Modern tech stack are inherently more fragile than the real legacy stuff. The Mainframe tech that powers visanet has enormous practical limitations. But holy crap is it stable. Something about the dozens of abstraction layers that hadn't been invented yet when the original ISO payment standards and processes were first invented. The very close to metal and low surface area for breakage. And the benefit of decades of experience in these legacy stacks to shake out bugs. All of Visa's global commerce literally runs through just one of seven (mostly one of three) physical computers. Crazy stuff. But probably not sustainable many more decades. Eventually core networks will have to migrate to modern hardware, OS and SW stacks. That migration could create a lot of benefits, but I would not expect that maintaining the currently observed ~5-7 nines reliability to be one them.
- galenmarchetti 3y agoI wonder how much of the stability is the extreme reluctance to do any upgrades or touch anything related to that mainframe code. In my experience with larger institutions using mainframes, its largely "code freeze, do not mess with it". I wonder if this is a consequence of the stability, or a cause of it? Modern tech stacks are always upgrading components underneath to remain modern and frequency of changes cause instability no matter how hard you try. Not really any meaningful tooling to get around that yet