How fast is vector search compared to traditional search?

Vector search is significantly faster than traditional keyword-based search when dealing with similarity queries in large datasets, but the comparison depends on the use case and implementation. Traditional search relies on exact matches or term frequency (e.g., TF-IDF) to find results, which works well for structured data but struggles with semantic meaning. Vector search, by contrast, uses mathematical representations (embeddings) of data to find items that are “close” in a high-dimensional space. This allows it to handle queries like “find images similar to this photo” or “find documents with related themes” efficiently. For these tasks, vector search often outperforms traditional methods because it avoids the need to scan every entry in a dataset—instead, it uses precomputed indexes optimized for similarity comparisons.

The speed advantage of vector search comes from specialized indexing techniques like approximate nearest neighbor (ANN) algorithms. For example, libraries like FAISS or Annoy create hierarchical or partitioned indexes that group similar vectors together, reducing the number of comparisons needed during a query. A traditional search over a database of 1 million text documents might require scanning every document for keyword matches, which scales linearly with data size. Vector search, using ANN, can achieve sub-linear time complexity by narrowing the search to a subset of candidate vectors. However, traditional search can still be faster for exact keyword lookups in small datasets, where inverted indexes (common in traditional systems) provide near-instant results without the overhead of vector preprocessing.

The trade-offs depend on the data type and query requirements. Vector search excels in scenarios where similarity matters more than exactness, such as recommendation systems or image retrieval. For instance, searching for a product in an e-commerce database using a text description (e.g., “comfortable running shoes”) benefits from vector search’s ability to match semantic intent, even if the keywords don’t align exactly. Traditional search, however, remains faster for structured queries like "WHERE price < 100 AND category = 'shoes’". Developers should choose based on the problem: vector search for semantic or unstructured data, traditional search for exact matches or structured filters. Hybrid approaches, combining both methods, are increasingly common to balance speed and accuracy.