[Question] Questions about Metrics Collection Architecture

### Question

I am curious about a few points related to the system architecture:
- Collectors can be scaled up easily, but what about the manager?
- If not, is there any plan to improve or change the architecture to better support horizontal scaling in the future?

- Is there a specific reason for using a persistent custom TCP protocol between the manager and collectors?
- Was using HTTP APIs considered but rejected due to performance or efficiency concerns?

Just wanted to understand the reasoning behind these choices and whether any future improvements are being planned in these areas.

Thanks in advance!

Start by reading the manager and collector architecture, focusing on how the persistent custom TCP protocol connects them and how HTTP APIs compare. Determine whether the project documents manager scaling, protocol rationale, or future architecture plans; done means providing or updating that explanation with the issue's questions answered.

Written by the indexing model from the issue text.