I used them this week for the first time and was impressed by the responsiveness on my phone. I looked into the network tab and what I saw was an over-the-wire solution.
However, I'm sure that you can also achieve responsiveness this without HTML over the wire. I scimmed a few blog posts, and it seemed to me like they use Java EE, although I'm not entirely sure.
I checked out the profile by their main software architect Guido Steinacker [1], their job offerings on otto.de [2], their github (they have repos for classic Java EE patterns, like their Wicket component tester and HAL stuff, which is a default in spring data) [3], and their stepstone, which mostly shows spring and java jobs [4]. There is no single asp.net job listed and they also don’t have anything asp.net related on their github. I don’t think that builtwith is an accurate data source.
I used them this week for the first time and was impressed by the responsiveness on my phone. I looked into the network tab and what I saw was an over-the-wire solution.
However, I'm sure that you can also achieve responsiveness this without HTML over the wire. I scimmed a few blog posts, and it seemed to me like they use Java EE, although I'm not entirely sure.