Maybe not the same story, but there was a sidecar service for encrypting traffic and doing access control and other things in a way that was transparent to the app (like Envoy, but without the mesh and much earlier). The original version was written by (maybe) a single engineer in Erlang. Version two was given to another team and rewritten in Java because. They had never tested at scale and every team I know who went to production with it fell over. There was some company wide deadline, but it was unusable, at the point, and the teams I was working with were gun shy to try it again since it was obvious that the owning team had know idea what the performance characteristics or system requirements were for it.

I think I switched teams before that was resolved and moved to some greenfield work where we didn’t have to worry about scale for a while, but I do believe they eventually figure it out.