RemoteIndian

I want to implement 15 day trial feature in my application any suggestions how can this be implemented? Should I store some trial field in user schema which will be set to true while registration but then after 15 days it will set to false and if payment is not done user should not to able to login.

Or may be tie your trial with a license, where your app only needs a valid license to function, and if license has expired (15 days in this case), your app would ask for a working license instead.

Depends on how deep you are willing to go. Not allowing login post trial would be bad for your conversion rates. Instead, you should allow login but block functionality and prompt to upgrade

For the actual mechanism, you can implement a user type/role field, and then implement a role based access in your APIs. This can be useful for other things in the future as well. But if you just want to do something quick, then you can just set a trial field as you said, and check for that while serving any requests you want to tie to that.