You haven’t seen or heard them because they are abstracted away by APIs, circuit breakers and proxies. Almost ALL banks, credit card companies, travel systems and other high throughput transaction systems run on mainframe that is written in COBOL.
I think the issue here is that people working in fintech don't seem to come across these systems much, if at all - if you know one specifically, please tell us.
It's still there at the accounting/backend level. Automated Financial Systems Level 3 and it's replacement Vision are commercial loan systems.
LVL3 is pure cobol. It has been recently deprecated but there are many banks who own the code and are still self hosting it, along with it's IBM green screen support.
Vision is a java front end in front of an updated cobol backend. When your reputation is based on your reliability and long term code stability, at what point do you risk making the conversion, versus training new developers to work on your system.
No, we are not afraid of our own systems. The idea that there is some fabled computer system which everyone is too scared to touch doesn’t exist (I work in payment processing). There are levels of controls way outside these systems which provide these safety nets (e.g settlement / reconciliation controls).
If the cobol is still there, it’s not due to risk. If anything, the cobol is a much higher operational risk than replacing it.
Analogously, GDSes like SABRE still ran on mainframes until very recently (c. 2023) [0]. SABRE was written in some combination of assembly and some kind of in-house dialect of PL/I, if I recall.
I worked briefly at a company that wrote applications that interacted with bank mainframes. Think end point bank teller systems and in branch customer/account management. They definitely do exist - every major bank has a mainframe written in (usually) cobol.
But it's very abstracted, part of our main product offering WAS abstracting it. On top of our ready to use applications, we offered APIs for higher-level data retrieval and manipulation. Under the hood, that orchestrates mainframe calls.
But even then that there could be more level of abstractions. Not every bank used screen-level mainframe access. Some used off the shelf mainframe abstractors like JxChange (yes, there's a market for this).
Fintech would be even more abstracted, I imagine. At that point you can only interact with the mainframe a few levels up, but it's still there. Out of sight.
