How do you make it so you can sign in with phone number for app?
<p>I am making an app and I want to know the overall jist to make it so you can sign in with your phone number. For example, in the app Down to Lunch (an app to invite your friends to get food), once you download it, the first thing you do is sign in with your phone number. From then on, your number is how you are identified in the app. What I want to know is once you submit that number, is it added to a table in a database? Then when a new user registers, that number must go through and check against every number in that table to make sure it is different? If so, wouldn't that take long for a large user base (like a social network) or is that just what databases are capable of doing? (more specifically amazon web services, because I would use their relational database service, im guessing)</p>