Vector search is an essential component of Generative AI applications, enabling AI models to understand which texts are semantically similar. pgvector is a Postgres extension that allows vector search, and its latest release includes a new graph-based index for approximate nearest neighbor (ANN) search known as Hierarchical Navigable Small Worlds (HNSW). HNSW makes vector search queries significantly faster and more responsive. It creates a multi-layered graph to quickly traverse layers to find approximate nearest neighbors, allowing developers to balance the trade-offs between index quality, query speed, and resource usage. While HNSW offers impressive speed, it provides approximate results, is resource-intensive, and can be complex to tune for optimal performance.