My app uses FCM legacy API to send notifications. But those APIs were deprecated on June 20, 2023, and will be removed in June 2024. In FCM Legacy Api I have used the following code to send notifications

I have multiple devices (both Android and IOS) subscribed to same topic (e.g. “all”/”unregistered”)
I am sending FCM notification through postman,
I am able to successfully able to receive notification on all devices, but when I add image url to notification all devices receive notification but some devices are showing notification image.

i am using Rest API using netty library along with vertx event loop handle the multithreading, how to generate the access Token use it across all the threads in vertx event loop. Any idea how to handle this scenario.
i am using below code to generate the token and generating the token in every 45 mins.

we are using Firebase HTTPV1 and i am under spark plan(No cost)
How many message can i send per day, per month and per second and i am using same project for all the push notifications and Is there any throttling on push message for FCM HTTPV1?
we are getting few message drops while doing more pushes via REST Call with java code

we know that access Token expiry was one hour, can i use refreshIfExpired() will it impact performance
if i create the access Token for first time to send it to REST Call, will create the token from service_account_key.json

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.