Since the Access token has expiration time of 60 minutes , one of the easy and better way would be use Cache and storing it into Cache for 30 mins rather than persisting it into a database.
This will also help in efficient call of API reducing the rate limit issue. Storing in DB will not be a good idea as it will be expiring after 60 mins and so no use of persisting it .
You can also generate the access token from refresh token whose expiration time is longer compared to access token
"other thing is can i get access token from back end without opening RingCentral Popup or login page ? "
For grant type =Authorization code, you will be compulsorily getting login page , but you can you can avoid it if you use grant type =Password
Using the RingCentral Phone for Desktop, you can dial or receive test calls, send and receive test SMS or Fax messages in your sandbox environment.
Download RingCentral Phone for Desktop:
Tip: switch to the "sandbox mode" before logging in the app:
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