You haven't done it, then. Just the re-testing of everything in these large companies is terrifying and complex. Particularly the real-time stuff like Kafka. Most companies refuse to update unless absolutely necessary as they see the solution as an investment that has to produce. Security concerns have changed that attitude somewhat, but you would be surprised how much re-work is often necessary. The frustration of sorting it all out is not worth the money, imho--I'd rather just do something else, so I am.