The Carto 2 project is part of the Geo-IDE program of the Ministries of Ecology and Agriculture in France. The objective of Geo-IDE is to provide stakeholders in the ministries with common data and tools in the field of geographic information. Since 2019, the Ministry of the Ecology and Camptocamp have been collaborating to create a new module, Carto2, that would allow data administrators to compose, publish and consult maps online and other users to search, consult or download published maps at the same time. Carto2 also had to offer a more modern and ergonomic platform, as well as possibilities to evolve the module and its functionalities in order to better meet the needs and expectations of the decentralized services. The project is developed using free solutions such as Geoserver, QGIS Server and Openlayers. This is an example of the development of a large departmental spatial data infrastructure used by about 150 services in France. We will present the software architecture and the strategies put in place to develop Carto 2 and we will describe the technical challenges we have faced during the development.