It's not the tech they are using but the size of the project. This project requires simple tasks but spread over multiple technologies such that most developers

It's not the tech they are using but the size of the project. This project requires simple tasks but spread over multiple technologies such that most developers won't have experiences with all (or even many) of them. The key thing here is the time. Having just done a ton of interviewing I can tell you that almost every code challenge has some form of this issue and so you learn to just multiply the time they say by 3-4 (as a rough average). Thus taking ones that say 'a few hours', which means a day or two at most, are feasible but the ones that say 'a day or two' or 'a weekend' are not. Also remember candidate are usually not only applying to your job. They will easily have 3-4 of these going in parallel and with each taking up that much time is untenable.