When you say databases, do you mean persisting data? Or a specific implementation?
For API calls, I assume your referring to REST APIs using JSON and such? There are good libraries for this depending on the language.
Discussion
I was trying to create a database for a high score board and tried using php/ MySQL. I would much rather use relays but couldn’t figure out how web hooks work.
As for APIs I was trying to use the LNbits API but ran into some problems running an instance on my mynode, could only get extensions working on legends.lnbits
Would like to learn more about Rest APIs and JSON files.
Recommend checking out:
https://www.freecodecamp.org/learn
Idk anything about PHP.
Specifically, I’d look at the DB and the API courses.