You don't always get to use a modern, popular STL. Sometimes you need to use the hardware vendor's crappy, unoptimized STL (because they assume you won't use it

You don't always get to use a modern, popular STL. Sometimes you need to use the hardware vendor's crappy, unoptimized STL (because they assume you won't use it). This is part of the reason the STL is unpopular in game development, though the story here has been getting better. To answer your question, in my experience when the standard doesn't mention the desired performance characteristics of a function or method, even the popular STLs (libstdc++ and libc++ certainly) optimize for maintainability over performance. Not sure I can pull up an example of this right now but they are numerous. A good place to start is the standard containers other than deque or vector. A bigger issue IMO is that the existence of some methods in various standard classes/templates really murder performance, no matter how good the implementation is. One particularly bad example is the bucket() method, local_iterator types, etc. in c++11's unordered_map (probably the rest of the unordered family too). These force the table to be implemented in such a way that every insertion requires a heap allocation, and iteration requires much more pointer chasing than would otherwise be necessary (e.g. with a probed implementation), which is... unfortunate for the cache.