Garnet is a remote cache-store from Microsoft Research that offers strong performance (throughput and latency), scalability, storage, recovery, cluster sharding, key migration, and replication features. Garnet can work with existing Redis clients.
DbUp is a .NET library that helps you to deploy changes to SQL Server databases. It tracks which SQL scripts have been run already, and runs the change scripts that are needed to get your database up to date.
Realm is a mobile database: a replacement for SQLite & ORMs
Smallest full text search engine (lucene replacement) built from scratch using inverted Roaring bitmap index, highly compact storage, operating in database and document modes