To get specific saved instrument for a customer id and instrument id
Sandbox and Production End Point
Sandbox End Point - https://sandbox.cashfree.com/pg
Make sure you generate credentials in the test dashboard.
Production End Point - https://api.cashfree.com/pg
To process live payments, make sure you use credentials from the live dashboard. Do not share your secret key with anyone.
Partner Authentication for API calls - More details available here.