It is not currently possible to store an application session via Server API / REST. If the application is closed, the session will be lost and the user will need to log in again.
The access via the application token is needed to read the app data and it has only READ access to resources.
The expiration time for the token is 2 hours after the last query (this is used for security reasons).
If you perform the query with an expiration token you will receive the "Required session does not exist" error. In this case you need to re-create the session.
As an option, we can increase the expiration time of application and user session tokens from 2 hours to more on the Enterprise server.
Feel free to check our official documentation for more information that will help you to integrate QuickBlox services into your applications / projects or contact our Support team by submitting a ticket if you have any other questions.