No doubt you could implement a modern web API in Ada, but you wouldn't really be playing to Ada's strengths. Ada is more commonly associated with safety-critical embedded work than with web development.
Ada Web Server (AWS) [0][1] is Free and Open Source software, but that framework doesn't seem to get much use, and it doesn't inspire confidence that [0] mentions SOAP but doesn't mention JSON. I'm not aware of any proprietary/payware Ada web server solutions.
Ada Web Server (AWS) [0][1] is Free and Open Source software, but that framework doesn't seem to get much use, and it doesn't inspire confidence that [0] mentions SOAP but doesn't mention JSON. I'm not aware of any proprietary/payware Ada web server solutions.
[0] https://www.adacore.com/gnatpro/toolsuite/ada-web-server
[1] https://github.com/AdaCore/aws