Multilayer tilesets can offer cost savings and performance improvements over multiple single-layer tilesets, but they are not appropriate for every use case. This guide outlines some of the factors to consider when you are deciding whether to create a multilayer tileset.
Multilayer tilesets are a good choice when you have multiple related layers that you want to include in the same style, since styles are more performant when they reference fewer tilesets. There is a limit to how many tilesets a style can reference, so multilayer tilesets also let you fit more data into a style.
You should not create a multilayer tileset if you don't intend to include the layers in the same style, since the unused data in the tileset can make the styles less performant.
When you update a multilayer tileset all the layers are re-processed, so all layers of a multilayer tileset should have similar update frequencies. For example, if you have some layers that are updated monthly and some that are updated daily, you should create two multilayer tilesets. Your daily updates will process quickly because they don't include unnecessary data, and you will save money by updating the monthly tileset only when you need to.
You can zoom in past the maxzoom of your tileset due to overzooming, which extrapolates the tile at the maxzoom to create additional zoom levels. Overzooming only applies to the overall tileset maxzoom, not the maxzoom for each layer, so if you have layers with different maxzooms and you want all the layers to be overzoomed, you should create separate tilesets.