A vector database is a specialized database management system designed to store, index, and query high-dimensional vectors efficiently. The choice of vector database can have a major impact on RAG (Recommendation and Analysis Graph) performance. When evaluating vector databases, several key factors must be considered, including open-source vs. private options, programming language support, licensing models, maturity, enterprise features, and performance metrics such as insertion speed and query speed. Various optimization techniques, cost-saving measures, and scalability strategies can further enhance the efficiency and effectiveness of a vector database in managing unstructured data. Understanding these technical criteria is crucial for selecting the right vector database and unlocking valuable insights from private data.