Who would host the index? You can't contact one million peers to run a search, so fanout-on-read doesn't work. If the index is also distributed (by search term

Who would host the index? You can't contact one million peers to run a search, so fanout-on-read doesn't work. If the index is also distributed (by search term?), then the search+indexing nodes will need to fanout-on-write, which is less latency-sensitive but still pretty onerous.