Koa is made by the same team that brought us Express. It’s faster and smaller, but requires more setup. The biggest difference you will notice is that instead of the usual (req, res) it has (ctx, next). Ctx stand for “context” and is an object that has both the (req, res) inside it. Next is just calling the next middleware.
Koa does not come with much out of the box. You need to basically install each package, such as “@koa/router” for routing requests.
Why?
Express works great, so why bother with learning Koa? Because I like fast things! Of course, not using a Node framework would be even faster once running, at the cost of a slower development time. I really enjoy Express, and if the original team saw the need to make a new framework I am assuming they had a good reason.