ServiceStack supports Partial Content Responses for services that return:
A Physical File
return new HttpResult(new FileInfo(filePath), request.MimeType);
A Memory Stream
return new HttpResult(ms, "audio/mpeg");
Raw Text
return new HttpResult(customText, "text/plain");
Static files served through ServiceStack
Partial Content is also available in static file downloads served directly through ServiceStack which lets you stream mp3 downloads or should you ever want to your static .html, .css, .js, etc.
Http Utils
See PartialContentResultTests.cs for examples of how to request partial downloads using ServiceStack's built-in HTTP Utils.