Aha! This is done in https://github.com/uktrade/mbtiles-s3-server https://github.com/uktrade/mbtiles-s3-server, but using an alternative library to query SQLite

Aha! This is done in https://github.com/uktrade/mbtiles-s3-server https://github.com/uktrade/mbtiles-s3-server, but using an alternative library to query SQLite on S3, https://github.com/michalc/sqlite-s3-query https://github.com/michalc/sqlite-s3-query (Full disclosure: I wrote most of both of these)