Mappy is an online mapping company based in France and fully-owned by Solocal Group (PagesJaunes). Mappy was the pioneer in online mapping in France, and holds a significant market share in France and Belgium (about 10 millions monthly users). The company has developed an home-made LBS platform since 1998. The mapping service delivers 100 millions tiles a day. At the beginning of 2012, Mappy decided to redesign its core mapping service to meet new business challenges. The company needed a more standard and open source solution. Developers and product managers have fallen in love with Mapnik (some for code and performance, others for the map display quality). The team made the decision to build the new mapping service around Mapnik and others open source tools like PostGIS. The project was challenging : we switched from a MSSqlServer database/home made mapping engine/Windows architecture to a postgis database/mapnik engine/Linux one. During the development, we've seen and appreciated the energy around Mapnik and we started to gradually dive into code and contribute to some features. This talk will present a feedback on the overhaul : the functional and technical challenges, the decision to contribute to Mapnik project, the release of this service, its performance and the future roadmap.