It's fascinating how Raft has democratized distributed computing -- writing a consistent, distributed state machine now can be done in a few lines of code, assuming you have a Raft implementation lying around, like Hashicorp's excellent Go library.
What this project (and similar projects such as Rqlite) doesn't address is the hard problem -- sharding. Raft makes it quite trivial to write a master/slave system where every node is guaranteed to be identical, but it won't scale writes and won't distribute storage across your cluster.
You can build sharding on top of Raft, but in an SQL setting this would require distributed transactions, something that's difficult enough that relatively few projects have tackled it so far, the notable ones being CockroachDB and TiDB. (Google Spanner, being proprietary, is not relevant in this context.)
What this project (and similar projects such as Rqlite) doesn't address is the hard problem -- sharding. Raft makes it quite trivial to write a master/slave system where every node is guaranteed to be identical, but it won't scale writes and won't distribute storage across your cluster.
You can build sharding on top of Raft, but in an SQL setting this would require distributed transactions, something that's difficult enough that relatively few projects have tackled it so far, the notable ones being CockroachDB and TiDB. (Google Spanner, being proprietary, is not relevant in this context.)