This is Time based OTP written in Java (Spring Boot) - API

References:

Github Repo: https://github.com/ralscha/springsecuritytotp
Demo: https://totp-omed.hplar.ch/index.html
Blog post: https://golb.hplar.ch/2019/06/totp-spring-security.html

Thanks to Ralscha (https://github.com/ralscha)