When comparing Hapi vs Koa, the Slant community recommends Hapi for most people. In the question“What are the best backend web frameworks?” Hapi is ranked 27th while Koa is ranked 33rd. The most important reason people chose Hapi is:
Hapi was developed and is still being used by Walmart. Being backed by such a major company means that it will not lose support any time soon and most importantly it's being developed by professionals and that you will always get support for it.
Specs
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Pros
Pro Backed by a major corporation
Hapi was developed and is still being used by Walmart. Being backed by such a major company means that it will not lose support any time soon and most importantly it's being developed by professionals and that you will always get support for it.
Pro Consistency across applications
Hapi's philosophy is that configuration is more important than code. This is especially useful for very large teams because it helps developers maintain consistency and reusability throughout their code.
Pro Generator support from ground up
Using generators (a bleeding edge feature, even for Node.js) would clean up your code from the mess caused by all those callbacks; making your code more manageable.
Pro Extremely lightweight
Koa is very lightweight with just 550 lines of code.
Pro async/await keywords are supported and has transcended beyond generator functions
Generators functions are of course a huge plus, but at the time Koa team has transcended generations functions and shifted towards async/await style programming. It has made the Koa best framework available in the market.
Pro Development team has a proven track record
Koa is developed by the team behind a widely used node.js framework (express.js).
Pro Built for ES6
Cons
Con Requires too much boilerplate
Hapi seems to be made with large applications in mind. The sheer amount of boilerplate code it requires is simply not practical for a small web app. This also means that there are few examples of Hapi applications around for beginners to learn from.
Con Community is relatively small
Con Not compatible with express style middleware
Koa uses generators which are not compatible with any other type of Node.js framework middleware.