Though if you have enough users pinging the server you'll probably end up with a bunch of operations happening, which do have fees. It may be better cost-wise to just put this SQLite database on D1 (especially if it gets read-only replication at some point) and set up a Worker to return tile data in one HTTP request. That way the infrastructure is still serverless, but doesn't require N requests per tile, just 1.
I'm not sure! I would imagine it's planned though, scaling to that size seems important for a database product. I'm not on the D1 or R2 teams so I'm not intimately familiar with their products.
We’ve been experimenting with R2 for serving tiles from an 80gb pmtiles archive, unfortunately the latency on up to 3 byte range requests from a worker is 5-10 seconds so it’s not practical for real usage yet. Can we expect that to improve as R2 gets closer to general availability?
(I also work for CF)