"the CA Certificate thing"? Please be more specific as to what "thing" you mean.

Certificates required when making https requests (google cloud functions)

Hello, I want to send data to Firestore Cloud Function, there will be thousands of mcu (esp). What are your suggestions on how to do the CA Certificate thing? The devices can be abroad, how should I organize this? If you have any resources etc. I would be very happy (I am thinking of using ESP32 ...