At the moment, maps servers host a geo database (postgresql) with an import of OSM data, an object store (cassandra) which stores the pregenerated vector tiles, the process to generate vector tiles (tilerator) and the process to serve raster tiles to the clients (kartotherian). The object store is very generic and is basically just a key-value store, not using any advanced feature of cassandra.

Since the object store has mostly nothing specific to maps, it would make sense to externalize it to a shared object store. The obvious candidates would be cassandra as used by restbase, swift, or a custom object store (@Eevans has some thoughts about this, I'll let him elaborate).

Any of those solution is likely to require some changes to tilerator / kartotherian, so it is likely to require some development time (and it is unclear if / when we can get access to dev resources for maps).

Some of the question we want to ask before getting further into this discussion:

• number of tiles needing to be stored
• overall storage size
• access patterns to the tiles (number of read / writes per seconds, taking into account that writes are async)
• access times expected from the storage
• ...