LynseDB

LynseDB is a Python-first vector database with a Rust storage and search engine, built for AI applications that need to move from a local prototype to a service, and then to a lightweight sharded cluster, without changing the client API.

It is a good fit for RAG, semantic search, agent memory, multimodal retrieval, document QA, recommendation features, and internal AI tools where you want strong retrieval primitives without operating a heavyweight database stack on day one.

LynseDB also searches more than embeddings: native distance paths cover geospatial coordinates, packed binary fingerprints, aligned numeric profiles, and probability distributions through the same collection API.

import lynse

client = lynse.VectorDBClient("./ai-memory")              # embedded
client = lynse.VectorDBClient("http://127.0.0.1:7637")    # server or cluster

Why LynseDB

• Start local, grow in place: use the same Python client for embedded storage, a single HTTP server, or a coordinator-backed cluster.
• Rust where it matters: vector storage, search, indexes, filters, WAL, snapshots, and server execution are backed by the Rust core.
• AI-native retrieval: dense vectors, metadata filters, BM25, hybrid search, sparse vectors, named vector fields, external reranking, and result views are exposed from one collection API.
• Domain-aware similarity: use Haversine for coordinates, packed Tanimoto/Dice/Hamming for fingerprints, correlation for aligned profiles, Hellinger/Jensen–Shannon/Wasserstein-1D for distributions, and Chebyshev/Canberra/Bray–Curtis for feature and abundance data.
• Small operational footprint: a single Python process can own the data directory during development; production can run as an HTTP service with API keys, health checks, readiness checks, metrics, OpenAPI, Docker, systemd, and Kubernetes examples.
• Cluster mode when one node is not enough: shard groups, stable hash bucket routing, coordinator fan-out search, replica write mirroring, health checks, primary promotion, and /cluster_info diagnostics are included.
• Cost-conscious by design: use local mode for notebooks, scripts, tests, jobs, and single-service apps; add network and cluster overhead only when multiple workers, larger datasets, or failover require it.

Install

Python 3.9 or newer is required.

pip install lynsedb

For document-first inserts and search(document=...), install the optional local embedding adapter explicitly:

pip install "lynsedb[embeddings]"

Native Linux and macOS environments are supported. Native Windows environments are not supported; on Windows, run LynseDB inside WSL 2 or use Docker.

Quickstart: Build a Tiny AI Knowledge Base

This example stores small knowledge snippets with documents and metadata, then retrieves context for a user question. LynseDB can embed the documents lazily through the default local FastEmbed adapter, build a FLAT-IP index on first write, and commit automatically when the collection context exits successfully. commit() is a fast logical write boundary; call checkpoint() before backups, snapshots, controlled shutdowns, or critical durability acknowledgements.

import lynse


docs = [
    {
        "id": "local-mode",
        "title": "Local mode",
        "text": "Use embedded mode for notebooks, tests, jobs, and single-process AI apps.",
        "tags": ["local", "python"],
    },
    {
        "id": "server-mode",
        "title": "Server mode",
        "text": "Run lynse serve when several services or workers need shared vector search.",
        "tags": ["server", "production"],
    },
    {
        "id": "cluster-mode",
        "title": "Cluster mode",
        "text": "Use a coordinator with shard groups when one node is not enough for data or throughput.",
        "tags": ["cluster", "scale"],
    },
]

client = lynse.VectorDBClient("./lynsedb-ai-demo")
db = client.create_database("assistant", drop_if_exists=True)
collection = db.require_collection("knowledge", drop_if_exists=True)

with collection:
    collection.add(
        ids=[doc["id"] for doc in docs],
        documents=[f"{doc['title']} {doc['text']}" for doc in docs],
        fields=docs,
    )

question = "How should I deploy vector search for multiple workers?"
result = collection.search(
    document=question,
    k=1,
    where="tags CONTAINS 'server'",
    return_fields=True,
)

for item in result.to_list():
    print(item["id"], item["title"], item["text"])

You now have the core loop behind most AI retrieval systems:

1. Chunk or collect content.
2. Embed it.
3. Store vectors with stable IDs and metadata.
4. Search by semantic similarity plus filters.
5. Send the returned fields to your LLM as grounded context.

For production systems, explicitly choose and version your embedding model. Pass vectors directly through vectors= when you already use OpenAI embeddings, sentence-transformers, FastEmbed, CLIP, or your own model.

One API, Three Deployment Shapes

1. Embedded Mode

Use embedded mode when one Python process owns the data directory. It avoids a network hop and is the fastest way to add vector search to a notebook, local agent, ingestion job, test suite, or single-process app.

import lynse

client = lynse.VectorDBClient("./data")

Do not share the same embedded data path between independent processes. When multiple processes need the same database, run the HTTP server.

2. HTTP Service Mode

Use service mode when web workers, background jobs, or multiple applications need shared access to one LynseDB instance.

lynse serve --host 0.0.0.0 --port 7637 --data-dir ./server-data

import lynse

client = lynse.VectorDBClient("http://127.0.0.1:7637")

With API key authentication:

lynse serve \
  --host 0.0.0.0 \
  --port 7637 \
  --data-dir ./server-data \
  --api-key your_key

client = lynse.VectorDBClient("http://127.0.0.1:7637", api_key="your_key")

Useful service endpoints:

curl http://127.0.0.1:7637/healthz
curl http://127.0.0.1:7637/readyz
curl http://127.0.0.1:7637/metrics
curl http://127.0.0.1:7637/openapi.json

3. Cluster Mode

Use cluster mode when a single server is no longer enough for data size, query throughput, or shard-level failover. Applications still connect to one endpoint:

client = lynse.VectorDBClient("http://coordinator:7637")

The coordinator owns metadata and request routing. Shard nodes are ordinary LynseDB HTTP servers, each with its own data directory.

Python / API clients
        |
        v
Coordinator :7637
        |
        +-- shard group sg0
        |     +-- primary http://10.0.0.11:7638
        |     +-- replica http://10.0.0.12:7638
        |
        +-- shard group sg1
              +-- primary http://10.0.0.21:7638
              +-- replica http://10.0.0.22:7638

Cluster workflow:

1. Start normal LynseDB servers as shard primaries and replicas.
2. Create a cluster.json that lists shard groups and replica layout.
3. Start a coordinator with --role coordinator.
4. Point application clients at the coordinator.
5. Monitor /cluster_info for shard health, replica state, and promotions.

Cluster mode does not require shared storage. Coordinator metadata is stored on metadata owner shard(s) over internal RPC, and --cluster-state is only a local cache path for the coordinator process. Make sure each coordinator can reach the metadata owner shard RPC ports. By default, clusters with three or more shard primaries use the first three primaries as replicated metadata owners; smaller clusters use the first primary. Pass --metadata-owners only when you want to pin the owner set explicitly.

lynse serve --host 127.0.0.1 --port 7638 --data-dir ./data/sg0-primary
lynse serve --host 127.0.0.1 --port 7639 --data-dir ./data/sg0-replica
lynse serve --host 127.0.0.1 --port 7640 --data-dir ./data/sg1-primary
lynse serve --host 127.0.0.1 --port 7641 --data-dir ./data/sg1-replica

lynse serve \
  --role coordinator \
  --host 127.0.0.1 \
  --port 7637 \
  --cluster-config ./cluster.json \
  --cluster-state ./cluster_state.cache.json

Cluster advantages:

• Horizontal data growth: stable hash buckets distribute collection records across shard groups.
• Parallel retrieval: searches fan out to shard groups and are merged by the coordinator into one top-k result set.
• Replica-aware writes: active replicas can receive mirrored writes when write_mirror_replicas is enabled.
• Failover foundation: the coordinator health-checks primaries and replicas; a healthy active replica can be promoted if a primary fails.
• No client rewrite: application code keeps using VectorDBClient and the normal database, collection, add, upsert, delete, search, and query APIs.
• Clear operations model: authoritative coordinator metadata lives on the metadata owner shard(s), while each coordinator keeps only a local cluster_state.cache.json cache.

Read the full cluster deployment guide before using cluster mode in production.

Retrieval Features

• Dense vector search with flat, HNSW, IVF, SPANN, DiskANN, and quantized index families.
• SQL-style metadata filtering through where expressions.
• BM25 search over metadata fields for exact and lexical recall.
• Hybrid search with reciprocal-rank fusion or weighted dense/text candidates.
• Named vector fields for multimodal records, such as text and image embeddings on the same item.
• Sparse vector search for feature-weight retrieval.
• External rerank hooks for cross-encoders, LLM rerankers, or business rules.
• ResultView objects with NumPy arrays plus list, JSON, and dataframe conversion helpers.

Search More Than Embeddings

Vector search is useful anywhere records can be compared numerically, not only after an embedding model:

The exact Flat path supports every metric above. HNSW supports L1, Haversine, correlation, Hellinger, Wasserstein-1D, Jensen–Shannon, and Chebyshev. Binary Flat search lazily packs each dimension to one bit, reducing the hot scan representation by 32x versus float32 for word-aligned dimensions without replacing the durable source vectors.

See Domain-aware distance metrics for input contracts and the index compatibility matrix.

Indexing

New collections build a FLAT-IP index automatically after the first primary vector write. Disable this with default_index=None, or choose another default when creating the collection:

collection = db.require_collection("docs", dim=384, default_index="FLAT-COS")

Call build_index() when you want to rebuild or switch index modes. Move to HNSW, IVF, or SPANN when latency matters, DiskANN when memory pressure matters, and quantized variants when you want a smaller memory or disk footprint:

collection.build_index("HNSW-L2")
collection.build_index("IVF-L2", n_clusters=256)
collection.build_index("SPANN-L2", n_clusters=256)
collection.build_index("DiskANN-L2")
collection.build_index("FLAT-IP-SQ8")
collection.build_index("FLAT-L2-PQ")

See the indexing guide for metric names, nprobe tuning, binary indexes, and quantized index variants.

Docker

docker run -p 7637:7637 -v lynsedb-data:/data birchkwok/lynsedb:latest
docker run -p 7637:7637 -e LYNSE_API_KEY=your_key -v lynsedb-data:/data birchkwok/lynsedb:latest

On Windows, use this Docker image or install/run LynseDB from a Linux environment in WSL 2.

Deployment examples:

• Docker Compose
• systemd
• Kubernetes
• Cluster deployment

Documentation

• Learning path
• Core concepts
• Quickstart
• Connect and deploy
• Databases and collections
• Add vectors
• Search and filter
• Domain-aware distance metrics
• Metadata filter cookbook
• Indexing guide
• Named, sparse, and hybrid search
• Build a RAG workflow
• Performance tuning
• Backup and maintenance
• Troubleshooting
• Client API
• ResultView

Stability Notes

LynseDB is evolving quickly. Pin package and server image versions for deployments, test migrations before upgrading, and back up data directories plus cluster state before operational changes. For concurrent production access, prefer the HTTP server or coordinator cluster over sharing one local data directory across independent Python processes.