@kisshoma - I found Relevanssi seemed to struggle with larger WP sites (which is something the plugin author even mentions). Our site has around 6000 posts and it seemed to kind of stall out. If you have a vps and the ability to install java and elasticsearch, I found Fantastic Elasticsearch to be an excellent plugin. With a few tweak I was even able to boost newer results based off of the date. Also searches are extremely fast.