Does anyone know the actual programming language(s) used to develop Amazon Alexa, not the skills but Alexa itself? I have been searching online but the answers I'm seeing are all related to Alexa skills' development.
I suppose there is not that one language.
First at all you have all the Natural language processing (NLP) and machine learning stuff. Most probably delivered by this team: https://www.amazon.jobs/en/landing_pages/amazon-aachen-development-center. See the job descriptions there - they are looking for experience in: "Java, C++ or Python".
You can also watch about job descriptions of the cambridge team: https://amazon.jobs/de/landing_pages/Cambridge. There are also some short videos.
Also the overall team https://www.amazon.jobs/en/teams/alexa-information is looking for similar languages. See the job descriptions there.