Note: This feature is an experimental one. It will be included in 4.1, but it will be behind an experimental feature flag. It is possible that this will change before full inclusion in the product.

RavenDB now supports multiple operating systems, and we spend a lot of effort to bring RavenDB client APIs to more platforms. C#, JVM, and Python are already done and Go, Node.JS, and Ruby are in various beta stages. One of the things that this brought up was our indexing structure. Right now, if you want to define a custom index in RavenDB, you use C# Linq syntax to do so. When RavenDB was primarily focused on .NET, that was a perfectly fine decision. However, as we are pushing for more platforms, we wanted to avoid forcing users to learn the C# syntax when they create indexes.

Source: DZone