OAuth (Access Token) Vs API Key

Question

I have came across lots of articles and many suggesting to use OAuth over API Key. From my understanding, in OAuth, we are finally getting access token and it is valid for m

Answer 1

You need OAuth only when you want to enable a user of your service to allow a third-party client application to access his/her data hosted in your service without revealing his/her credentials (ID & password) to the application.

What a pair of API key & API secret can do is just authentication of a client application. If it is okay for you to allow an authenticated client application to access a user's data without explicit consent by the user, you don't have to use OAuth.