ProxySQL is a very powerful tool for the MySQL database. In simple words, it can tweak your MySQL when you have problems with slow queries or even it can be some kind of bridge between your MySQL databases placed in different localizations. Like in the name, it is a proxy, it’s placed between MySQL and application.
Sphinx is an open source full-text search server. Working with Sphinx is pretty much as with a database server . If you consider how to upgrade search engine in your application it can be an easiest way and number of relevance functions ensures you can tweak search quality as well.