The Foundation of RAG
Every RAG system depends on a vector database to store embeddings and perform similarity search at query time. The database choice affects retrieval latency, accuracy, operational complexity, and cost. With over a dozen options on the market, each with different strengths, the selection decision requires understanding your specific scale, query patterns, and infrastructure preferences. We evaluate candidates against your actual requirements rather than relying on vendor-published benchmarks.
Pinecone
Fully managed, serverless vector database. Zero operational overhead. Strong performance at any scale with automatic indexing. Best for teams that want to avoid managing database infrastructure entirely. Higher per-query cost than self-hosted options.
Weaviate
Open-source vector database with built-in vectorization modules. Supports hybrid search (vector + keyword) natively. GraphQL API. Self-hosted or Weaviate Cloud. Best for teams that want integrated embedding and search in one system.
Qdrant
Open-source, Rust-built for performance. Advanced filtering during vector search without post-filtering penalties. Payload indexing for metadata-heavy workloads. Best for applications requiring complex filtered similarity search.
pgvector
PostgreSQL extension adding vector similarity search to your existing Postgres database. Zero additional infrastructure. HNSW and IVFFlat indexes. Best for teams already on PostgreSQL that want to avoid adding another database to their stack.
Selection Process
Requirements
Scale, latency, filtering needs
Benchmark
Test candidates with real data
Evaluate
Ops complexity and total cost
Deploy
Production setup with monitoring
Requirements
Scale, latency, filtering needs
Benchmark
Test candidates with real data
Evaluate
Ops complexity and total cost
Deploy
Production setup with monitoring
Vector Database Comparison
Detailed Comparison
Each vector database makes different tradeoffs. The right choice depends on which tradeoffs align with your priorities.
Milvus. Distributed vector database designed for billion-scale datasets. GPU-accelerated indexing and search. Kubernetes-native deployment with horizontal scaling. Most complex to operate but handles the largest datasets. Best for organizations with 100M+ vectors and dedicated database operations teams.
Chroma. Lightweight, developer-friendly vector database. Embeds directly in Python applications with SQLite backend. Excellent for prototyping and small-scale deployments (under 1M vectors). Not recommended for production workloads requiring high availability or horizontal scaling.
pgvector vs dedicated vector DB. pgvector handles up to 5-10 million vectors well on a standard PostgreSQL instance. Beyond that, dedicated vector databases provide better query performance due to purpose-built indexing. If you are already on PostgreSQL and your dataset is under 5M vectors, pgvector avoids the operational cost of another database entirely.
Selection Criteria
We evaluate vector databases across dimensions that matter for production RAG systems.
Query latency at scale. p95 latency for top-10 nearest neighbor search at your expected dataset size. Most databases perform well at 1M vectors. The differences emerge at 10M-100M+ vectors where indexing strategy and hardware utilization determine performance.
Filtered search performance. RAG queries often filter by metadata (date range, document type, department) before similarity search. Some databases apply filters after vector search (losing relevant results), while others integrate filtering into the search process. This distinction significantly affects retrieval quality.
Operational complexity. Pinecone: zero ops. pgvector: PostgreSQL ops (which you likely already do). Qdrant/Weaviate: moderate containerized ops. Milvus: significant Kubernetes ops. Match the operational requirement to your team's capability.
Who This Is For
Vector database selection is for organizations building RAG systems or semantic search applications. If you are evaluating vector databases and want an unbiased comparison based on your specific dataset size, query patterns, and infrastructure preferences, we provide the benchmarking and analysis to support a confident decision.
Contact us at ben@oakenai.tech
