instant.page (mentioned in another response) is popular, but it’s not the only game in town. Google Chrome Labs made an alternative called quicklink which also attempts to optimize CPU time by preloading in-viewport pages during idle time. instant.page generally expects you to be using a mouse; results on touchscreens are pretty minimal and probably not worth the extra JS.
Speculation rules are being standardized for a JavaScript-free alternative. Figuring out which pages to preload will be the hard part. I like this because it’ll be easy to globally disable the behavior if I need to save data (or if it helps reduce fingerprinting).
If your backend isn’t too slow and your payload is small, simpler optimizations are probably better.