Hey @Nima1, I can start to answer some of these questions:
Yes, it’s possible. You can set the chat channel retention days to “0” to retain messages forever — but given the scale of what you’re doing, you’re right to wonder about performance impacts. I’ll also note that we do not currently support searching chat messages (it’s on our minds but is not currently planned). This means that even if you are retaining messages forever, given your high project usage, it may not be feasible for members to find specific messages.
I’m not positive about the answers to these questions, let me check with some of the engineers who have worked on chat the most to see what they think.
I’d also love to learn more about your use case — would you be willing to share some more detail about what you’re working toward?