That's why I like the idea of scoped executors rather than trying to have a global executor do everything. Libs should provide their own executors and manage their own async event handling while allowing the user to provide their own implementation if needed (e.g. for single threaded test code where performance is not a problem or e.g. in a production environment where you can heavily optimize the executor if your requirements demand it). If you don't call any of the async overloaded functions in a lib, then you don't get any of the async code compiled in, including the runtime.