Out of curiosity, how is the 92% recall calculated? For a given query, is the recall compared to the true topk of all 100B vectors vs. recall at each of N shards compared to the topk of each respective shard?

(author here) The 92% mentioned in this post is showing recall@10 across all 100B vectors, calculated by comparing to the global top_k.

turbopuffer will also continuously monitor production recall at the per-shard level (or on-demand with https://turbopuffer.com/docs/recall). Perhaps counterintuitively, the global recall will actually be better than the per-shard recall if each shard is asked for its own, local top_k!