Marketing Cloud REST API Authentication Tokens Expiring before 60 Minutes
|Knowledge Article Number||000230262|
For Fuel/REST API, access tokens expire one hour after they are issued. If you attempt to use an expired token, you'll receive a "401 Unauthorized HTTP" response. When this happens, you'll need to refresh the access token.
You shouldn't request a new token for every API call made, as each token is good for an hour and should be reused. Making two API calls for every one operation is inefficient and may result in throttling.