Add Rostam vector database integration

integrations/rostam-document-store.md

@@ -0,0 +1,66 @@
+---
+layout: integration
+name: Rostam
+description: Use the Rostam vector database with Haystack
+authors:
+  - name: RostamLabs
+    socials:
+      github: rostamlabs
+pypi: https://pypi.org/project/rostam-client/
+repo: https://github.com/rostamlabs/rostam
+type: Document Store
+report_issue: https://github.com/rostamlabs/rostam/issues
+version: Haystack 2.0
+toc: true
+---
+
+An integration of [Rostam](https://rostamlabs.com) — a high-performance vector
+database and sub-microsecond key-value store in a single Go engine — with
+[Haystack](https://haystack.deepset.ai/).
+
+`RostamDocumentStore` stores Haystack `Document`s in a Rostam collection and runs
+dense similarity search over them; `RostamEmbeddingRetriever` is the matching
+retriever component for Haystack pipelines. Rostam can be embedded as a library,
+run standalone (REST / gRPC / TCP), or replicated across a Raft cluster, and adds
+HNSW/IVF/Vamana indexes, quantization, hybrid dense+sparse and BM25 search, and
+metadata filtering.
+
+## Installation
+
+```bash
+pip install "rostam-client[haystack]"
+```
+
+Point it at a running Rostam server:
+
+```bash
+docker run -p 8080:8080 -e ROSTAM_API_KEY=secret ghcr.io/rostamlabs/rostam:latest
+```
+
+## Usage
+
+```python
+from haystack import Document
+from rostam.haystack import RostamDocumentStore, RostamEmbeddingRetriever
+
+store = RostamDocumentStore(url="http://localhost:8080", collection="docs")
+
+# Write documents (each Document must carry an embedding)
+store.write_documents([
+    Document(content="Rostam is a vector database and KV store in one Go engine.",
+             embedding=[0.1, 0.2, 0.3]),  # from your Haystack embedder
+])
+
+# Retrieve in a pipeline
+retriever = RostamEmbeddingRetriever(document_store=store, top_k=5)
+results = retriever.run(query_embedding=[0.1, 0.2, 0.3])
+```
+
+Pair `RostamEmbeddingRetriever` with any Haystack embedder (or Rostam's built-in
+pure-Go local embeddings) in a retrieval or RAG pipeline. See the
+[Rostam docs](https://docs.rostamlabs.com/) for server setup, indexes, hybrid
+search, and filtering.
+
+## License
+
+`rostam-client` is available under the Apache-2.0 license.