This reminds me of a system I worked on, the devs all developed locally with all the services but in prod the services were on different hosts and the performance was terrible.

This reminds me of the system I worked on, the devs had promised a 3-tier system but delivered a 2-tier system so management had them add a middle layer and the performance was terrible.

This reminds me of the system I worked on, the devs decided a lockless architecture was the way for better performance but with the limited threads we had at the time, apart from the few people who kept hold of a thread until they were done, the performance was terrible.

This reminds me of the system I worked on, the database design was a serious bottleneck but no one wanted to fix that so the app tier tried to change their queries, the performance was terrible.

I don't know why people spend so much time optimizing the wrong thing - it happens over and over again!