turbopuffer v3 demotes the vector index to a secondary index

turbopuffer, the search layer behind Cursor and Notion, announced that in v3 the vector index stops being the primary data structure and becomes just another secondary index. The reason is write amplification: updating one vector can move hundreds of attributes. The new engine is currently slower and still being tuned.

• In v3 documents are keyed by stable ID; ANN index becomes secondary
• turbopuffer serves billions of vectors for Cursor and 10B+ for Notion
• Claimed: 100B+ vector indexes, 200 ms p99 reads, 1k+ QPS
• v3 is currently a significant performance regression, tuning underway