Started with Python + Django + MySQL, hosted on PythonAnywhere.

At some point, decided to rewrite the project from scratch in Clojure using MongoDB, since Clojure was much better suited for solving the problem in question (modelling the grammar of a natural language - https://www.pealim.com) and MongoDB was better suited for the constantly evolving grammar spec. The rewrite took around two months and I believe that it was the right decision, though I still miss some of the things that Django provides for free (like the admin interface and user authentication).

I also use ClojureScript + Reagent, though not yet on the user-facing parts of the app.