Blast is a full text search and indexing server, written in Go, built on top of Bleve.
Phalanx is a cloud-native distributed search engine that provides endpoints through gRPC and traditional RESTful API.
Cete is a distributed key value store server written in Go built on top of BadgerDB.
Cockatrice is a full text search and indexing server. It is written in Python built on top of Whoosh.