Last I checked, Sphinx had a huge design flaw in that it indexed directly from an SQL database. In other words, your Sphinx configuration not only needs to have read access to the database, it needs to contain the required SQL queries.

This tightly couples Sphinx to your application and your schema, and creates serious issues for your ops team since every app change potentially needs to modify the Sphinx config. It gets particularly hairy when you want to host multiple applications using a single Sphinx daemon.

We started out with Sphinx for our apps but quickly discarded it in favour of ElasticSearch, a much more elegant and orthogonal piece of software.