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====== Vector Database Comparison ======

A practical guide to choosing the right vector database for AI agents, RAG systems, and semantic search. Current as of Q1 2026.

===== Vector Database Comparison Table =====

^ Database ^ Language ^ Stars ^ Hosted Option ^ Max Vectors ^ Filtering ^ Hybrid Search ^ Pricing ^
| **FAISS** | C++ (Python bindings) | 33k | No (library only) | Unlimited (RAM-bound) | Post-filtering only | No | Free / open-source |
| **Milvus** | C++ / Go | 35k | Yes (Zilliz Cloud) | Billions (distributed) | Yes (scalar pre-filter) | Yes (dense + sparse) | Free OSS; Zilliz from $0 free tier |
| **Qdrant** | Rust | 25k | Yes (Qdrant Cloud) | Billions (on-disk + distributed) | Yes (advanced payload) | Yes (dense + sparse + BM25) | Free OSS; Cloud from $25/mo |
| **ChromaDB** | Python | 18k | Yes (Chroma Cloud beta) | Millions (RAM-limited) | Yes (metadata) | Partial | Free OSS; Cloud in beta |
| **Weaviate** | Go | 20k | Yes (Weaviate Cloud) | Billions (cloud-native) | Yes (GraphQL filters) | Yes (BM25 + vector) | Free OSS; Cloud free tier available |
| **Pinecone** | Proprietary | N/A (closed) | Yes (fully managed) | Billions (serverless) | Yes (metadata) | Yes (sparse-dense) | Pay-as-you-go; free tier 1M vectors |
| **pgvector** | C (Postgres ext) | 14k | Via Postgres hosts | Billions (with partitioning) | Yes (full SQL) | Partial (pair with tsvector) | Free OSS; hosted via Supabase/Neon etc |

===== When to Use Which =====

<mermaid>
graph TD
    A["Choosing a<br>Vector Database"] --> B{"What stage<br>are you at?"}
    
    B -->|"Prototyping /<br>Local dev"| C{"Need persistence?"}
    C -->|No| C1["FAISS"]
    C -->|Yes| C2["ChromaDB"]
    
    B -->|"Production /<br>Scale"| D{"Self-host or<br>managed?"}
    D -->|"Self-hosted"| E{"Primary<br>requirement?"}
    E -->|"Performance"| E1["Qdrant"]
    E -->|"Scale + ecosystem"| E2["Milvus"]
    E -->|"GraphQL API"| E3["Weaviate"]
    
    D -->|"Fully managed"| F{"Budget?"}
    F -->|"Minimize ops"| F1["Pinecone"]
    F -->|"Cost-conscious"| F2["Qdrant Cloud or<br>Weaviate Cloud"]
    
    B -->|"Already using<br>Postgres"| G["pgvector"]

    style A fill:#4a90d9,color:#fff
    style C1 fill:#2ecc71,color:#fff
    style C2 fill:#2ecc71,color:#fff
    style E1 fill:#e67e22,color:#fff
    style E2 fill:#e67e22,color:#fff
    style E3 fill:#e67e22,color:#fff
    style F1 fill:#9b59b6,color:#fff
    style F2 fill:#9b59b6,color:#fff
    style G fill:#e74c3c,color:#fff
</mermaid>

===== Detailed Guidance =====

=== Prototyping & Local Development ===

  * **FAISS** -- Best for experimentation. Facebook's library gives you raw speed with zero infrastructure. No server needed, just ''pip install faiss-cpu''. Downside: no persistence, no filtering, no API.
  * **ChromaDB** -- Best for quick RAG prototypes. Embedded mode with persistence. Simple Python API. Not built for production scale.

=== Production Self-Hosted ===

  * **Qdrant** -- Written in Rust for performance. Excellent payload filtering. On-disk storage means you can handle datasets larger than RAM. Strong hybrid search with BM25.
  * **Milvus** -- Battle-tested at billion-scale. Horizontal scaling via distributed architecture. Zilliz Cloud for managed option. Most mature open-source vector DB.
  * **Weaviate** -- Go-based with a rich GraphQL API. Built-in vectorization modules (no need to pre-compute embeddings). Excellent hybrid search.

=== Fully Managed ===

  * **Pinecone** -- Zero ops. Serverless scaling. Best if you want to focus purely on your application logic. Trade-off: vendor lock-in, no self-host option.

=== Already Using Postgres ===

  * **pgvector** -- Add vector search to your existing Postgres. No new infrastructure. Full SQL filtering. Best when vectors are a feature, not the whole product. Combine with ''tsvector'' for hybrid search.

===== Performance Characteristics =====

^ Database ^ Indexing ^ Query Latency ^ Memory Efficiency ^ Disk-Based ^
| FAISS | HNSW, IVF, PQ | Sub-ms (in-memory) | Moderate | No |
| Milvus | HNSW, IVF, DiskANN | Low ms | Good (segment-based) | Yes |
| Qdrant | HNSW | Low ms | Excellent (Rust) | Yes |
| ChromaDB | HNSW | Low ms | Moderate | Limited |
| Weaviate | HNSW | Low ms | Good | Yes |
| Pinecone | Proprietary | Low ms | N/A (managed) | N/A |
| pgvector | HNSW, IVFFlat | Moderate ms | Depends on Postgres | Yes |

//Last updated: March 2026//
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