Hacker News Reader

You can make up API calls which you can say you'd implement later. As long as these are not tricky blocks, you'll be fine.

For Google, Facebook and Amazon, yes. At least last I interviewed there a few years ago. They're more interested in the data structure/algorithm

But I have also been to places that demand actual working code which is compiled and is tested against cases

Usually there the problem is simpler, so there's that