Hundreds of millions of dollars have gone into vector database startups. The model's first answer is a Postgres extension.
We ran fifteen buying questions through grounded search — the questions a real buyer types, not keywords — and recorded which tools the answers named and which sources they cited. 32 distinct sources, 117 citations. What follows is that data.
What AI models actually name
| Tool | Mentions |
|---|---|
| pgvector | 15 |
| Pinecone | 15 |
| Postgres (also cited as PostgreSQL) | 15 |
| Qdrant | 15 |
| Weaviate | 15 |
| Milvus (also cited as Milvus/Zilliz) | 13 |
| Chroma | 10 |
| Redis | 7 |
| Turbopuffer | 6 |
| Cloudflare Vectorize | 3 |
| Elastic (also cited as OpenSearch/Elasticsearch) | 3 |
| MongoDB Atlas Vector Search | 3 |
| LanceDB | 2 |
| Vespa | 1 |
Five names were tied at the top, each appearing in all 15 answers: pgvector, Pinecone, Postgres, Qdrant and Weaviate. A Postgres extension sits alongside the funded, dedicated databases — not beating them, but equally present in every single answer.
That is worth sitting with if you are building infrastructure. Models are grounded on what people write about, and people write about the thing they already had. Being the obvious extension of a tool developers already run gets you into the same set as a company that raised nine figures to compete with it.
It also shows the shape of the whole dataset: models do not rank, they enumerate. Five in every answer, and the other nine names we found in barely any. The gap is not between first and second. It is between being in the set and not.
Where the answers come from
These are the pages the models cited most. The top three carry 32% of all citations in this category, and Reddit threads carry 23% across 9 separate discussions.
Method
Fifteen buying questions, run through grounded search on 3 September 2026:
What are the best Vector Databases For AI brands? · Which Vector Databases For AI should I buy? · Best Vector Databases For AI for beginners · Most trusted Vector Databases For AI brands and why · Compare the top Vector Databases For AI brands · What Vector Databases For AI do experts recommend? · Best value Vector Databases For AI · Which Vector Databases For AI brands have the best reviews? · Top rated Vector Databases For AI 2026 · What should I look for when choosing Vector Databases For AI? · Alternatives to the most popular Vector Databases For AI · Is there a better option than the leading Vector Databases For AI brand? · What do people on Reddit recommend for Vector Databases For AI? · Best Vector Databases For AI for small businesses · What's the highest rated Vector Databases For AI right now?
Every answer carries citations. We recorded all of them and ranked by frequency.
What this does not do. We did not test these tools, run trials, or compare features hands-on. Plenty of roundups claim they did. We measured which tools AI models recommend and which sources those recommendations came from — a different question, and the one that matters if your goal is being recommended rather than choosing.
Reproducibility. Ask the same questions again and substantially the same sources come back. In our testing, two independent runs of a category minutes apart returned the same URLs in the same order.
This is one of seven categories we mapped the same way. Across all seven, Reddit carried 16-27% of citations and the top three sources carried 29-33% — every single time.
This source map was made with Mayin.
Every number above came from running real buying questions through grounded search and recording what the answers cited. You can get the same map for your own category and brand in about 15 minutes, for $49 — one payment, no subscription, delivered in Telegram.