[mschuster91]

> A rewrite or a replatform is very, very hard and risky as a result; the system is now defined by how the mainframe runs the processes, to a very large degree.

And that's why so many neo-banks/fintechs are eating the lunch of the established banks left and right, same for insurance. The "old guard" is unwilling to pay the costs of not just upgrading off of mainframes (aka the rewrite work itself)... but of changing their processes. That is where the real cost is at:

When you have 213.000 employees like BoA has and everyone needs to have at least 10 hours of training and 2 weeks until they're familiar with the new system enough to be fully productive, that's like 2 million man-hours just for training and 16 million hours in lost productivity, so assuming $50/h average salary it's around 900 million dollars in cost. Unfortunately for the dinosaurs, the demands of both the customers and (at least in Europe) regulatory agencies especially for real-time financial transfers just push the old mainframe stuff to limits, while at the same time banks don't want to cede more and more of that cake to Paypal and friends that charge quite the sum for (effectively) lending money to banks.

In contrast, all the newcomers start with greenfield IT, most likely some sort of more-or-less standard SAP. That one actually supports running unit and integration tests automatically, drastically reducing the chance of fuck-ups that might draw in unwanted regulatory attention.

[jeremyjh]

BOA doesn't train the vast, vast majority of its workforce on mainframe systems these days. No one working in a branch or call center is looking at green screens anymore. The mainframe systems are simply used as back-ends connected through web services (yes, even in CICS!) or MQ Series and the like to web GUIs.

Source: worked there for many years, and built some of those integration systems.

[panopticon]

Eh, I think the tech stack is less important than the legal and regulatory structure.

Most fintechs aren't banks and partner with a Real Bank™ to provide the actual bank accounts. Fintechs are under much less regulatory scrutiny (for now—that may be changing with recent, high-profile screwups) and can move with much more freedom regardless of the tech stack they've chosen.