a large number of threads will be created when use sendEach api

[ffyyhh995511]

firebase-admin-java, the version is 9.3.0. When sendEach api is used to push tens of thousands of tokens, a large number of threads will be created, resulting in a high cpu. How do I solve the problem

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[lahirumaramba]

We are working on adding http/2 support to sendEach to solve this issue and improve performance. In the meantime, you can try implementing your own code to use the REST endpoints with http/2. We will track any progress on this here #979