FR: limit cost for reading unchanged data

Hello,

Scenarios were data do not change a lot are common cases, and Firebase is very expensive in these situations.
I understand that an "out of the box" solution is very difficult to implement (from your answer here: https://github.com/firebase/firebase-js-sdk/issues/3422)

In May, I was requesting the addition of a "source" parameter for the onSnapshot that would give devs the opportunity to optimize themselves the requests: https://github.com/firebase/firebase-js-sdk/issues/3040

Do you have more insights on this?

Thanks