What would the RL use case be for running this server, whose purpose is to facilitate transferring files from one computer's filesystem to another, on an ephemeral filesystem?
If what's meant here is that it would be hard to run this on a container platform because of the ephemeral nature of containers, assumably you would be using persistent volumes to keep your state safe across the container lifecycle.
That being said if you really wanted to use sqlite for the database, you'd do the exact same thing, use a persistent volume.
I wrote an interface that would allow SFTP transfer to Azure Blob Storage (doesn't support it) that doesn't store anything on the machine running the service. It was really just supposed to be a frontend.