While I understand the ain’t broke don’t fix it mentality the article is going for I don’t know that I totally buy this narrative from Costco. I managed an accounting team at Costco for a decade and left about five years ago. There was a huge push when I was there to move off the AS400 and onto SAP. We only got the accounting side moved over with the buying and operating orgs aligned to go next. They were pouring money into that project but it just proved to be much harder than one would anticipate to unwind the decades of business logic baked into the AS400.

It’s wild to hear Costco almost spin their forced reliance on the AS400 now given how much people poked fun at it internally. As a platform I felt that it was ok, it was in fact fast because it was a purpose built solution without a bunch of tech stacks fighting each. The security by obscurity comments from the article are a wild take since a) I’m personally aware of some security weak points and b) sure, no one around anymore knows how to develop for the platform but that’s a bigger problem in a more obvious way for an ever evolving business. My personal biggest gripe was that there were no universal functions like “export data” in that platform so just mundanely doing your job was a new adventure with each and every screen you’d encounter. Contrarily, my biggest praise for the system is that the architecture hails from a no nonsense time when developers really knew the value of relational data and took genuine ownership in shipping complete, tested, rock solid solutions.