A long these lines if you're looking for a way to sync your SQLite DB to an S3 like object store there is https://litestream.io/.
It creates a snapshot of your DB on s3 and then handles checkpointing of the WAL.
Litestream author here. I haven’t looked at Durable Objects yet so I don’t think Litestream would currently work with it. I may add support in the future but I’m adding separate serverless functionality to be released later this year. That’ll allow Litestream to run on Cloudflare Workers or GCR or other ephemeral platforms like those.