mbtiles-spec VS mbutil

This is definitely possible. A very common use case is publishing custom vector tiles to Mapbox, but since you want to host the tileset itself on your own server, you can use something like tilelive to do so. It's easy to create your own custom .mbtiles with Mapbox Studio, but it's an open specification, so feel free to create your own from arbitrary geographic data.

Prepare "MBTiles" to store map tiles built-in SQLite for conversion of COMTiles.

> I once experimented with using SQLite as a file store for small images

Mapbox productionized this with their MBTiles [0] format, to store millions of small vector or raster map tiles in an SQLite database. Much easier to work with than millions of images on disk.

[0]: https://github.com/mapbox/mbtiles-spec

Some background on mbtiles files from mapbox/mbtiles-spec

Then use Mapbox's own utility for parallel processing into your output: https://github.com/mapbox/mbutil

There is also an alternative to just unpack the files and serve it form the /priv/static folder. To serve it this way we need mb-util app installed - The files are compressed, so we need either unpack them or rename to have .gz extension - then phoenix will serve it gzipped and add the header for us.