Issues is after migrating from Legacy API to FCM HTTPV1 API.
We are Sending Push messages using REST API with json payload and Authorization done via access_Token
and we are creating access_Tokens in multiple-thread for same Service_Account_Key from FCM Project.
We are Generating access_Token every 30 mins for API authorization.
Each thread has it’s own access token, can we do this for pushing messages.

Can we create the multiple access token using same service_account_key since it we are using multi-threading? what is the expiry time for each token