This. Banks can't have extended downtime. So if a $100M budget would get a new system built, then what they would need is a $200M budget ($100M to run legacy i

This. Banks can't have extended downtime. So if a $100M budget would get a new system built, then what they would need is a $200M budget ($100M to run legacy in prod + $100M to build new system and gradually migrate). The only good in-house systems I've ever seen we're (a) based on vendor reference designs w/ minimal changes, (b) based on OSS, (c) architected by some very smart people who stay at the company for non-monetary reasons. Because when you boil it down to it, no company is big enough to solve a problem better than a group working with multiple companies (unless the problem is trivial). Or to word it another way, are you bigger / better / smarter than both of your top competitors put together? If no, then don't reinvent the wheel.