Qdrant

Qdrant is a vector similarity search engine built for RAG systems at scale, and honestly every AI company building LLM apps is going to need something like this eventually. They're optimizing around HNSW graphs to solve the latency and recall problems that pop up when you're searching through billions of embeddings, which is basically the problem every founder working on AI retrieval is going to hit. It's infrastructure-y and unsexy, but it's the kind of thing that becomes genuinely essential once your app actually gets traction.