How API providers handle webhook callback functions ?

I'm curious about how API providers handle the storage and manipulation of data in webhook callbacks. Specifically:

1. How do they store the data received in the callback? Is it stored temporarily or persistently, and how is it managed in a scalable way?
2. What mechanisms do they use to ensure that only specific, relevant data is manipulated or processed (e.g., ensuring data integrity and preventing unintended changes)?
3. How do they track and verify the callback data to ensure that it’s not tampered with before being processed?
4. Are there best practices or standards for securing and organizing webhook data to ensure privacy and accuracy?

I'd appreciate if know more if anyone have experience