Sqlite on the server is a fantastic starter database. Dead simple to set up, highly performant and scales way higher (vertically) than anyone gives it credit for.
But there certainly is a point you'll have to scale out instead of up, and while there are some great solutions for that (rqlite, litefs, dqlite, marmot) it's not inherent to Sqlite's design.
Replication means writing queries which alter the data to multiple machines, right?
Shouldn't that be done by a software one level up? Which takes in the queries via some network protocol and then sends them to all machines.
That would sound more logical to me.
It's fine to want to separate those out, but it's not easy to do so and there are reasons they've been coupled for decades.
Having a single DB that takes write queries via a proxy which spreads them out to multiple read-only-DBs sounds easy at first.
What do you do about out-of-sync read replicas?
ACID gets real hard real fast when introducing replication.
Sending a UPDATE/INSERT/DELETE statement to SQLite is not blocking? I would think it is, because in my code I can read the number of affected rows right after I sent the query.
> What do you do about out-of-sync read replicas?
Delete them and replace them by uploading a checkpoint and replaying a log of the queries since then.
Without that you will have drift from your master database.
With that, you have a whole new host of synchronization issues you need to deal with.