There are a wide range of tiny operating systems that can boot in a matter of milliseconds.
The applications are "whatever you want imagine" but yes one application is building FAAS Function As A Service in which the operating system carries out a single function.
Put anther way, Docker is complex, overweight, and requires re-implementation of much computing infrastructure. You can meet many of the same goals as Docker in much more simple way not by building containers but by building tiny operating systems.
I'm somewhat amused by the idea of booting an operating system from scratch to service a single request being described as "much more simple" than the alternative of, y'know, having a single instance serve many requests.
From an ops perspective, spinning up an instance to process a single request seems like
1) a complete and utter nightmare to debug.
2) A huge waste of computing resources. Even with a unikernel you're wasting time initialising resources and getting in to a ready state to be able to process a request. Why bother when you can be ready and respond effectively instantly?
OS does not serve requests -- applications do. While it may be possible to demo a toy OS+app, real-world applications take seconds if not minutes to start and warm up. Throughput on a cold-cache is a fraction of that on a warm cache.
Starting in milli-seconds is not the hard problem. Starting + warming caches in that time is -- that will get you a bunch of awards when you solve it.
Docker is just a manager of Linux namespaces. You'll need one to manage your operating systems anyway - start/stop them, copy them to the machine, delete them, etc.
The applications are "whatever you want imagine" but yes one application is building FAAS Function As A Service in which the operating system carries out a single function.
Put anther way, Docker is complex, overweight, and requires re-implementation of much computing infrastructure. You can meet many of the same goals as Docker in much more simple way not by building containers but by building tiny operating systems.