Hello,
I am really curious to learn about Wolfram Alpha and its back-end technology. Any pointers where I can learn about it?
Best, Vijay
The back end technology of Wolfram|Alpha is Wolfram Language. You could start reading about or developer page, or API docs, or about grammar, - etc. - just search Wolfram sites. Also consider applying for Wolfram Innovation Summer School where hands on projects are done.
You can start from a collection of Stephen's blogs. Especially:
Also some posts by Michael Trott where he talks about integration in Wolfram Language.
Here is a schematics pinpointing the difference between Wolfram|Alpha and Watson from one of Stephen's posts.