> What's preached against is not performance, but a performance-first attitude.
That's what's preached against in theory. But in practice any performance discussion is immediately met with that answer. The standing recommendation is build it fully ignorant of all things performance, and then hope you can somehow profile and fix it later. But you probably can't, because your architecture and APIs are fundamentally wrong now. Or you've been so pervasively infested with slow patterns you can't reasonably dig out of it after the fact. Like, say, if you went all in on Java Streams and stopped using for loops entirely, which is something I've seen more than a few times. Or another example would be if you actually listen to all the lint warnings yelling at you to use List<T> everywhere instead of the concrete type. That pattern doesn't meaningfully improve flexibility, but it does cost you performance everywhere.
That's what's preached against in theory. But in practice any performance discussion is immediately met with that answer. The standing recommendation is build it fully ignorant of all things performance, and then hope you can somehow profile and fix it later. But you probably can't, because your architecture and APIs are fundamentally wrong now. Or you've been so pervasively infested with slow patterns you can't reasonably dig out of it after the fact. Like, say, if you went all in on Java Streams and stopped using for loops entirely, which is something I've seen more than a few times. Or another example would be if you actually listen to all the lint warnings yelling at you to use List<T> everywhere instead of the concrete type. That pattern doesn't meaningfully improve flexibility, but it does cost you performance everywhere.