Well that was always something the nostr protocol was going to have to handle if its supposed to be a true alternative to Twitter. 

If the protocol can't scale to that size without a few massive relays doing all the work, then it's Bluesky with extra steps and a muuuuuuuuch shittier UX. That means it's not a serious global social network IMO, moreso one for niche communities only, just like Mastodon is looking to be.