In previous version of QGIS, the snapping index cache was built sequentially and you had to wait for all your layers to be indexed before starting edition. Thanks to the QGIS.org grant program, QGIS now builds the snapping index cache in parallel for each layer, so it speeds up the whole process. Snapping has also been relaxed, meaning that you don't have to wait for the cache to be complete, you can start editing and snapping information will appear as soon as they are ready.