[Foivos]

I think it is very unlikely for a conversation to reach billions of messages. There are less than 32 million seconds in a year. So, Yoigo would need to send a message per seconds for decades to reach a billion.

Of course there are people who are much more popular than me, so it might be possible and I am not aware of it. :)

[aaomidi]

These are channels and groups with thousands of members.

https://t.me/durovschat Has 9500 members

https://t.me/swhkdemocracy Has 6000 members

https://t.me/linux_group Has 6000 members

https://t.me/PublicTestGroup Has 18000 members

There is no limit to joining these chats. These design decisions Telegram has picked has allowed the app to be quasi social media, rather than just IM. You can't index these and maintain chat history locally. You'd need way more bandwidth and energy and computational power than the average cellphone has.