kitio.aiFaiss vs MongoDB Atlas Vector Search
A side-by-side look at pricing plans, free tiers, features, pros and cons, updated for 2026. Faiss is completely free, while MongoDB Atlas Vector Search is freemium.
At a glance
Best for
Category
Pricing model
Starting price
Free plan
Made by
Based in
Rating
Key features
- Nearest neighbor search
- Clustering
- GPU algorithms
- Python wrappers
- Indexes larger than RAM
- Evaluation tools
- Vector indexes in Atlas
- Hybrid text and vector search
- Voyage AI embeddings
- Automated embedding
- Document filtering
| Feature | Faiss | MongoDB Atlas Vector Search |
|---|---|---|
| Best for | Open-source library for similarity search over dense vectors | Vector search built into MongoDB Atlas with Voyage AI embeddings |
| Category | Models & APIs | Models & APIs |
| Pricing model | Free | Freemium |
| Starting price | Free | See pricing page |
| Free plan | Yes, fully free | Yes |
| Made by | Meta FAIR | MongoDB |
| Based in | United States | United States |
| Rating | No ratings yet | No ratings yet |
| Key features |
|
|
Pricing compared
Faiss is completely free, while MongoDB Atlas Vector Search is freemium.
Free plan
Cheapest paid plan
Top plan
Free trial
4 plans
Free
Free
- 512 MB storage
- Shared RAM and vCPU
- Free forever
Flex
$0.011/hr, up to $30/mo
- 5 GB storage
- Shared RAM and vCPU
- Billed by ops/second tier
Dedicated
From $0.08/hr
- 10 GB to 4 TB storage
- 2 GB to 768 GB RAM
- Starts at about $57/mo
Enterprise Advanced
Contact sales
- Self-managed MongoDB
- Search and Vector Search add-on
- Consultative support
Prices in USD, checked Oct 28, 2026 or later. Plans change often, so confirm on each tool's site before you buy.
Pros and cons
Faiss
- Free and open source
- Scales past available memory
- GPU support for key algorithms
- A library, not a managed service
- Needs engineering effort to deploy
- Not a database, so no built-in server or storage
MongoDB Atlas Vector Search
- No separate vector store
- Strong embedding models included
- Free tier for testing
- Best if you already use MongoDB
- Search nodes add cost
- Some features in preview
Which one should you choose?
Choose Faiss if you want:
- Free and open source
- Scales past available memory
- GPU support for key algorithms
Watch out: a library, not a managed service.
Choose MongoDB Atlas Vector Search if you want:
- No separate vector store
- Strong embedding models included
- Free tier for testing
Watch out: best if you already use mongodb.
Faiss vs MongoDB Atlas Vector Search FAQ
What is the difference between Faiss and MongoDB Atlas Vector Search?
Faiss: Open-source library for similarity search over dense vectors. MongoDB Atlas Vector Search: Vector search built into MongoDB Atlas with Voyage AI embeddings. Both are models & apis tools.
Is Faiss or MongoDB Atlas Vector Search cheaper?
Faiss is completely free, while MongoDB Atlas Vector Search is freemium.
Do Faiss and MongoDB Atlas Vector Search have free plans?
Faiss: Yes, fully free. MongoDB Atlas Vector Search: Yes.
Who makes Faiss?
Faiss is made by Meta FAIR, based in United States.
Who makes MongoDB Atlas Vector Search?
MongoDB Atlas Vector Search is made by MongoDB, based in United States.
Which should I choose, Faiss or MongoDB Atlas Vector Search?
Choose Faiss if you value free and open source and scales past available memory. Choose MongoDB Atlas Vector Search if you value no separate vector store and strong embedding models included.