And a topk of 30 also means reranking of any sort is out, except for maybe limited reranking of 30->10, but that seems kind of pointless with today’s LLMs that can handle a bit more context.

Yeah exactly, so you could do something like shard by the first 4 bits of md5 of the text (gives you 16 buckets) but now you’re adding extra complexity to work around their limitations.