Ok, so there are a couple of downsides that should be kept in mind. Now the first is costs. But knowing I have just said a scary word, let me add that these costs are overblown by some. Some development studios are counting in a factor of four times more expensive. But I think this is not accurate. I think if done well you can actually save time.

Creating two separate entities always entails more configuration, scaffolding and maintenance. But benefit of having two entities though is that there is a lot of flexibility. A CMS can be changed for another, or a different frontend can be made based on the same CMS. This is something that was not even covered so far: A front-end can combine even multiple sources or a the data from several back-ends AND/OR the same back-end can be used in multiple front-end applications. So isn’t that just blowing your mind right now.

Anyways, back to the downsides. Another thing is hosting. Hosting a JavaScript framework can sometimes be a bit more costly because certain server configurations have to be made to get it to work. But this is a disappearing problem because even the more traditional hosting is finally catching up with reality.

Another downside is that some functionalities are a little easy to build when a site is made in the traditional way. Because what is older has been around longer. Especially php based platforms have a lot of battle tested functionality that is sometimes hard to emulate with a JavaScript framework. But in the best scenario, the front-end and back-end work in a good tandem, so the front-end offloads the hard stuff to the back-end that takes care of things. With mutual respect. The challenge is that this tandem needs to be crafted by able developers. Meaning custom code.