K-Nearest Neighbors, From Iris Flowers to Reverse Image Search

K-Nearest Neighbors Is the Cockroach of Machine Learning. It Will Outlive Us All. The algorithm behind the For You page, Spotify Discover Weekly, every reverse image search you’ve ever run, and the retrieval inside ChatGPT is older than color television. K-Nearest Neighbors. Proposed by Evelyn Fix and Joseph Hodges in a US Air Force technical report in 1951. Never really replaced. Just renamed, sped up, and quietly stuffed into every vector database you’ve heard of. Pinecone. Weaviate. Qdrant. Chroma. Milvus. All of them. Same idea, faster index.