[overgard]

Yes and no; we all know the Knuth quote etc, but there are a lot of design decisions you have to make up front (language, database, server, framework, etc.) that you can't change later, but which will set the floor and the ceiling for what your performance looks like.

For instance, if you're working in a resource constrained environment, garbage collected vs not garbage collected is a big decision. Or if you're working on a web app, how you layout your database tables or your nosql equivalents is going to have a huge effect, and is much harder to change later.

There's a huge difference between premature optimization vs making decisions that will have performance consequences down the road. If you wait till the end of a project/release cycle to think about performance, the amount you can do about it will usually be disappointing.