Mem0
Open-source persistent memory layer that gives AI agents the ability to remember users, preferences, and context across sessions. Supports vector, graph, and key-value storage backends. AWS partner for Strands Agents. YC W23, $24M raised, 30K+ GitHub stars.
Qdrant
Rust-based vector database optimized for filtering. Supports named vectors, payloads, and hybrid search. Self-hostable or cloud.