I've been working with Net Talk web server for around 10 years now. In that time I have made one very large web server, and several smaller ones.
I'm a firm believer that complexity in code is preferable to complexity to the end user. Though I do love it when I can make both simple.
I have interfaced with several 3rd party apis. Most http(s) based, but a few have Component Object Model or DLL. Most recently I made an interface to Quick Books Online.
I have also written interfaces to payment processors, both web based, and local using a credit terminal.
Check out me website
https://www.bisware.ca/.