Vector databases excel at storing and querying high-dimensional vectors, enabling AI-driven applications to find semantic similarities that traditional query methods simply cannot detect. Document databases shine in their ability to store semi-structured data in flexible, JSON-like formats, making them ideal for applications with evolving schemas and nested data structures. The lines between these database types are blurring as applications increasingly need both semantic understanding and flexible document storage. Vector databases are adding vector capabilities, while document databases are enhancing their ability to store and query document metadata alongside embeddings. For developers and architects building applications in 2025, understanding when to use each database type—and when they might complement each other—has become crucial for creating systems that can effectively handle both traditional document operations and modern AI-powered functionality.