Allow users to search/query/filter posts by custom fields

Hi all,

I’d like to have a front-end search were users can query posts according to custom fields/custom taxonomies – say from drop down menus or select boxes etc. But I can’t really find any plugins that would make this work, nicely. What i’m after seems pretty common – just like the search functionality that you’d find on sites like Yelp. I’m sort of wondering if this is something that is so easy for most developers that no one has developed a simple plugin for it?

I’m currently using Caspio but I’d like to move to a system based off of WordPress posts.

Anyone have any suggestions of how I might do this? Or if there is a suitable, up to date, good plugin?

Many thanks!