WordPress website. The client has requested that the content of the post should open in a pop-up on the same page. To do this, I make an ajax request to the server, which takes some time. I wanted to somehow optimise this process and thought about caching.

Options:

1. Localstorage. It's possible, but I have some doubts, because such data have no shelf life + content of whole post is quite voluminous data.
2. Window.Cache. I don't fully understand this method, but it seems acceptable.
3. Php cache. Classic option, but I don't like that processing will take place on server - it will still take some time, right? Did I understand correctly that in order to set up caching via PHP, you need to download caching tool packages (like Memcache)?

Can anyone suggest solutions to this problem? Maybe there are some better options that I haven't considered?