It's built on top of Tantivy (https://github.com/tantivy-search/tantivy) that implements Tha Raft Consensus Algorithm (https://raft.github.io/) by raft-rs (https://github.com/tikv/grpc-rs) and The gRPC (HTTP/2 + Protocol Buffers) by grpc-rs (https://github.com/tikv/grpc-rs) and rust-protobuf (https://github.com/stepancheg/rust-protobuf).