To play devils advocate: we must be careful about what we mean by "optimizations". If a problem is not completely understood, then it may be better to stay in a

To play devils advocate: we must be careful about what we mean by "optimizations". If a problem is not completely understood, then it may be better to stay in a high level language like Java so that one can rapidly iterate, than it would be to drop down to a strictly performance language, like Rust or C. It is far easier to downcode some service in a well architected Java system than it is to iterate a Rust system. It's also way better to have a working system that can be made cheaper by downcoding, than it is to have an optimal system that can't do the job because of its architecture. Also, within the last few years I have written assembly for an application originally in Java, so that's still on the table. =)