Credit unions and small banks outsource almost all of their core systems to companies like Fiserv. Literally thousands of banks and CUs all ride their infrastructure
I ran a website for a local CU for about 10 years. It was pretty fun doing things for their website that made their Fiserv web tools look like they were from 1970.
There was no interaction with user or account data on my end, just CMS-building, letting them go crazy with coupon promotions or pet shelter PSA's or warnings about ATMs being down, etc. They'd pitch me on a new project, I'd send them a timeline, and we'd add new features or tools to the website. I even hired a local college student to create some super-basic but useful financial tools for the site.
I loved how small-town-feel the whole thing was. At the beginning of the relationship, they gave me a list of broad requirements like "SAS-70", I found a DC to match, I sent them a contract, and I couldn't believe I actually had a banking institution as a client, 4 years out of school and a brand-new business owner.
Eventually they merged with another CU and went away, but apart from the very occasional "server down" notifications while I was on vacation, those are some really fun memories.
