You probably already know this, or are talking about another language, but JavaScript is inherently single threaded, so unless you’re running blocking I/O in parallel, you won’t actually see any performance boost. Service workers get their own thread though.

Then Promise.all is for you!

Await is usually there either because the performance doesn’t matter and the legibility is much higher with it, and/or because there are a series of asynchronous actions that depend on each other and await lets you write them as if they are sync because related to each other they are.