Embeddings and vector search: retrieval by meaning
An embedding turns a piece of text into a list of numbers positioned so that similar meanings sit close together. Searching that space is what lets a model be handed the three relevant paragraphs out of a million, and it is the infrastructure underneath most retrieval systems.
In one sentence
An embedding is a fixed-length numeric vector representing the meaning of a piece of text or other content; vector search finds the stored vectors nearest to a query vector, retrieving by similarity rather than by exact terms.
Keyword search fails when the question and the answer use different words for the same idea. Embeddings solve that by mapping meaning into geometry: a model trained for the purpose places semantically similar passages near each other, so proximity in the vector space stands in for relevance.
At scale, comparing a query against every stored vector is too slow, so systems use approximate nearest-neighbour indexes that trade a small amount of recall for very large speed gains. That trade — and the fact that it is a trade — is the single most important thing to understand about vector search.
How it works
How the index works
The common structures are navigable small-world graphs, which link each vector to its neighbours so search walks toward the query, and clustering schemes that partition the space and search only nearby partitions. Both are approximate: they find most of the true nearest neighbours most of the time, and the tuning knob is how much recall you will give up for latency.
Chunking decides quality
Documents must be split before embedding, and the split is consequential. Chunks too small lose the context that makes a passage meaningful; too large and the vector averages several topics into something that matches nothing well. Most disappointing retrieval systems have a chunking problem, not a model problem.
Hybrid retrieval usually wins
Pure vector search is weak on exact identifiers — part numbers, names, error codes — because those carry little semantic signal. Production systems combine keyword and vector scoring and often re-rank the combined candidates with a more expensive model, which reliably outperforms either method alone.
What this depends on
Technology dependencies are solved by engineering; supply dependencies are solved by building something, which takes years.
Technology
Embedding models
Retrieval quality is bounded by the model producing the vectors; changing it invalidates every stored vector and forces a full re-index.
Every document has to be run through the embedding model once, and again whenever the model changes. Re-embedding a large corpus is a scheduled compute project, not a background task.
Beyond a certain corpus size the index no longer fits in memory and part of it is served from solid-state storage. The drive's random-read latency then sets the tail latency of retrieval.
What each company supplies at this step, and — where a public figure exists — its share of this specific market — with what that share measures, the period it covers and who published it. Some rows also show the company’s own reported revenue for the segment covering this step, which is a different thing: it says how much this business matters to that company, not how much of the market it holds. Not a ranking and not a recommendation.
Added vector search to the database so retrieval does not require moving the records out of it.
What would change the picture
Whether vector search stays a separate product category or is absorbed into general-purpose databases.
Whether very long context windows reduce the need for retrieval, or simply raise the cost of not retrieving.
Whether re-indexing cost becomes a practical brake on adopting better embedding models.
Questions people ask about this
Do I need a dedicated vector database?
Often not. Established databases and search engines have added vector indexing, and for collections up to tens of millions of vectors that is usually adequate. A dedicated system earns its place at large scale, or when the workload is almost entirely similarity search.
Why is retrieval quality usually the problem, not the model?
Because a model can only work with what it is handed. If retrieval returns the wrong passages, a better model produces a more articulate wrong answer. In practice most retrieval failures trace to chunking, to missing keyword matching, or to no re-ranking step — not to the language model.
Each page explains one technology in plain language, states what it depends on, and names companies by what they supply at that step. Company roles are described qualitatively and deliberately carry no market shares, revenue figures or rankings — those change faster than an explainer can, and a stale number is worse than none. Ticker links point at company pages on this site and are provided for reference only.
Nothing here is investment advice, a recommendation, or a forecast. A company named on a page about a technology is not thereby a good investment, and the chokepoints described are structural facts about supply chains rather than predictions about prices. Technology moves; where a page describes something as unresolved or in development, that was true when it was written.