NosDB is described as '100% native .NET Open Source NoSQL Database (released under the Apache 2.0 License). NosDB is extremely fast and linearly scalable and allows your .NET applications to handle extreme transaction loads (XTP)' and is an app in the development category. There are more than 10 alternatives to NosDB for a variety of platforms, including Windows, Linux, Mac, BSD and Web-based apps. The best NosDB alternative is MongoDB, which is free. Other great apps like NosDB are CouchDB, Apache Cassandra, FerretDB and Azure Cosmos DB.