The CARTO team is optimizing PostGIS performance, focusing on reducing database query execution time to improve map rendering speed. They've identified two key areas for improvement: Mapnik rendering and MVT (Vector Tile) rendering. To optimize Mapnik rendering, they've modified the `ST_AsTWKB()` function to minimize memory allocations for small objects like points, and changed the implementation of `ST_Simplify()` and `ST_RemoveRepeatedPoints()` functions to reduce copying data around. For MVT rendering, they've made changes to the `ST_AsMVTGeom()` function to avoid unnecessary copying and polygon validity checks, which resulted in significant performance gains. These optimizations aim to improve map rendering speed while maintaining performance for other use cases.