Bing uses a lot of Microsoft technologies including C# and .NET framework languages but as with many large services (or sets of services in this case) the components crawling, processing, indexing and serving content are written in a variety of languages including C, C++, etc and are managed by a myriad of tools languages that support features.

A little googling finds: http://research.microsoft.com/en-us/news/features/fsharp-041...

"We’ve also seen fantastic applications in server-side data analysis, including in parts of the Bing ad delivery and analysis pipeline. F# seems a particularly good language for programmatic machine learning."

I think that is just one small part of the Bing system though.

That's Microsoft Research. There's no real direct pipeline from MSR to production.

Edit: To clarify, I know MSR is using F# in a lot more places than we are.

Parts of Bing are (were?) backed by Hadoop thanks to Microsoft's purchase of Powerset - all their NLP search technology ran on Hadoop.

I don't think this is true anymore... I think we're using COSMOS now? Maybe someone else wants to help me here.

I expect under the hood Bing is Azure.

Not much (the real-time Twitter results is one such piece). You have to remember that Bing predates Azure by many years. There is a lot of code/idea sharing though.

Azure is too new to be used by much in terms of internal MS. It's usually the other way around (other MS software is being used to power Azure).