CartoDB has been optimizing its map tile rendering process to improve performance, specifically by reducing the workload on the CPU. The team identified that the most significant bottleneck was the rendering of map tiles, which can be complex and time-consuming. To address this, they explored various techniques using PostGIS functions such as ST_SnapToGrid, ST_Simplify, and ST_SimplifyPreserveTopology to simplify geometries and reduce the number of input vertices. The results showed that applying these simplifications significantly reduced rendering times, with some levels seeing a reduction of over 90%. The team also contributed a patch to Mapnik to expose a style file parameter for automatic simplification based on resolution, which is expected to be released in CartoDB 1.0 and will benefit both CartoDB and OpenStreetMap users.