SOI samples used during the devsummit Extending ArcGIS for Server session in Berlin on November 12, 2015.
They are Server Object Interceptor and are written in C# using the ArcObjects .Net SDK
The samples that you will find there are "Proof of concept" : they are basic, not optimized, and will not take every cases and possibilities into account.
They should be used as simple samples to get started on :
- How you can develop an SOI.
- What you can do with them.
- and then of course, build great stuff !
To put things into context, the heatmap was developed during my plane trip to Berlin using literally the first lib that I've found to generate an heatmap in c#.
- FilterAccessSOI : Filter layer visibility of your services based on the ArcGIS platform user credentials
- heatmapSOI : Generate a server-side heatmap map, based on your point data.
(C#) ArcObjects Help for .NET developers
(C#) Developing server object interceptors help (with samples)
(C#) A blog post from Domenico Ciavarella (NicoGis) with samples about filtering access and map watermark
(Java/Scala) A project from Mansour Raad about generating on the fly images using MemSQL
Random points inside a Web AppBuilder application 
The server side heatmap inside a Web AppBuilder application
More explanation on how everything works, should be done in some days.