# Weaviate vs Milvus: Technical Trade-off Teardown

> Schema-first hybrid search ergonomics (Weaviate) versus maximum-scale index
> engines (Milvus / Zilliz Cloud) — compliance, scale and portability compared.
Last verified: 2026-10-09

**TL;DR** — Choose **Weaviate** for developer ergonomics: schema/multi-tenancy
first-class, built-in hybrid (vector + BM25) retrieval, and modules that wrap
popular embedding providers. Choose **Milvus** when scale and index variety are
the bottleneck: distributed architecture to 100M+ vectors, the widest index-type
coverage (HNSW, IVF family, DiskANN, GPU), and a compliance-heavy Zilliz Cloud
option. Full figures: [comparison matrix](/matrix.md).

## 1. Architecture at a glance

| Dimension | [Weaviate Cloud](/go/weaviate) | [Milvus (Zilliz Cloud)](/go/milvus) |
| :-- | :-- | :-- |
| Core engine | Open-source (BSD-3), Go | Open-source (Apache-2.0), C++/Go |
| Deployment | Weaviate Cloud (WCS), K8s operator, Docker | Zilliz Cloud (managed), K8s (Helm/operator) |
| Storage/compute | Tighter coupling; single-node or replicated | Decoupled: WAL + object storage + compute nodes |
| Index | HNSW (default) or flat/exact | HNSW, FLAT, IVF_FLAT, IVF_SQ8, IVF_PQ, DiskANN, GPU indexes |
| Metadata filtering | Post-filtering with inverted-index candidate filtering | Post-filtering with over-fetch + bitmap filtering |
| Hybrid search | Native hybrid mode (BM25 + vector, fusion ranking) | Sparse-vector/BM25 hybrid since Milvus 2.5 |
| Multi-tenancy | First-class (collection-per-tenant, HNSW allow-lists) | Partition keys / multi-tenant collections |
| Max vector dims | 65,535 | 32,768 |
| Compliance (cloud) | SOC 2 Type II | SOC 2 Type II, HIPAA, ISO 27001 |

## 2. Where each engine wins technically

**Weaviate — ergonomics and hybrid retrieval**

- Object-oriented schema: vectors, properties and references live in one store, so
  RAG pipelines can filter and fetch in a single query.
- Hybrid mode with BM25 fusion is one API call — no client-side reranking glue.
- Built-in vectorization modules (or bring-your-own embeddings) shorten prototypes.
- Post-filtering means broad filters can over-fetch; selective filters rely on
  metadata indexes to prune candidates.

**Milvus — scale and index choice**

- Distributed by design: WAL in message queue, vectors in object storage, index
  nodes scaled independently — a clean path past a single node's memory ceiling.
- Choose the index per workload: HNSW for latency, IVF_PQ for memory-tight recall,
  DiskANN for cost-efficient large corpora, GPU indexes for throughput.
- Multi-partition + partition-key sharding supports filtered searches across
  very large multi-tenant corpora.

## 3. Pricing & commercial terms

| Term | [Weaviate Cloud](/go/weaviate) | [Milvus (Zilliz Cloud)](/go/milvus) |
| :-- | :-- | :-- |
| Free tier | 14-day trial cluster (1 GB) — not a permanent free tier | Free Serverless tier (shared resources, limited RUs) |
| Minimum monthly spend (paid) | $0 — serverless usage-based | $0 — serverless usage-based; dedicated clusters hourly |
| Unit rates | Storage + operations based; dedicated pods billed hourly | Request units + storage; provisioned clusters hourly |
| Cost shape | Simple for small/medium corpora | Better $/vector at large scale with right index choice |

## 4. Compliance & residency

| Requirement | Weaviate | Milvus / Zilliz |
| :-- | :-- | :-- |
| SOC 2 Type II | ✅ | ✅ |
| HIPAA (BAA) | ❌ (verify current WCS terms) | ✅ |
| ISO 27001 | ❌ | ✅ |
| Data residency | 5 regions (AWS/GCP) | 10+ regions (AWS/GCP/Azure) |

Regulated workloads (healthcare, finance) currently favour Zilliz Cloud on paper;
re-verify against vendor trust centers before procurement (see [limits](/limits.md)).

## 5. Decision guide

Pick **Weaviate** if:

- Your app is schema/property-heavy and hybrid retrieval should be one API call.
- You value a small operational surface and want the option to self-host trivially.
- Corpus fits comfortably on a single (replicated) node.

Pick **Milvus** if:

- Corpus or QPS needs distributed storage/compute separation.
- You want index-type freedom (DiskANN/IVF/GPU) tuned per cost/latency target.
- Enterprise compliance (HIPAA/ISO) via a managed cloud is required.

Migration notes: export from Weaviate as `(id, vector, properties)` and upsert into
Milvus collections with a partition key for tenancy; re-run hybrid recall tests —
fusion ranking differences (Weaviate RRF vs your Milvus weighting) change ranking
more than the raw vectors do.

Related: [Pinecone vs Qdrant](/vs/pinecone-vs-qdrant.md) · [limits](/limits.md) · [matrix](/matrix.md)