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Vector Database: How to Choose the Right Solution for an AI or RAG Project

Auteur n°3 – Benjamin

By Benjamin Massa
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Summary – To succeed with your AI and RAG assistants, ensure relevance, speed, and reliability of vector retrieval while anticipating scale, latency, and document governance. A vector database indexes embeddings for semantic search, scales via monolithic or distributed architectures, and combines dense, sparse, or hybrid search with metadata filtering to balance performance and compliance. Your choice depends on data volume, target latency, access rights, and ecosystem maturity—from quick POCs (Chroma, pgvector) to managed services (Pinecone, Qdrant) or R&D options (FAISS, Milvus). Edana guides you from assessment to production, helping you select and deploy the optimal database without vendor lock-in.

Many companies are embarking on building AI assistants, intelligent search engines or Retrieval Augmented Generation (RAG) tools to leverage their document repositories. However, simply connecting a language model to a PDF or a SharePoint library is not enough.

You must first efficiently store, index and query embeddings—the numerical vectors that represent your business content. This is where the vector database comes into play: it becomes the critical component ensuring the relevance, speed and reliability of AI responses, both in production and in proof-of-concept (POC).

Role of a Vector Database in RAG

A vector database stores numerical representations of unstructured objects to enable semantic similarity search. It serves as the essential entry point for retrieval in a RAG system, determining the quality and reliability of the responses.

Definitions and How It Works

A vector database is designed to ingest and manage vectors generated by embeddings. These vectors result from applying an encoding model (text, image, audio) that transforms business content into fixed-dimensional vectors.

Unlike a relational database, it optimizes searches based on vector proximity using metrics such as cosine distance, inner product or algorithms like HNSW and IVF. It finds content that “means roughly the same thing” rather than content containing exactly the same words.

In practice, each document is split into chunks (paragraphs, support tickets, product datasheets) and then encoded. The vectors are indexed in the database to accelerate queries while retaining associated metadata for subsequent filtering.

Role in a RAG System

In a RAG workflow, the AI model does more than generate text from its internal knowledge. It first queries the vector database to retrieve the most relevant passages.

These passages are inserted into the prompt to enrich the context of the large language model (LLM), enabling it to produce a response based on controlled, up-to-date and private information. Retrieval relevance directly affects the quality of the final answer.

If the database returns an outdated or irrelevant document, the AI can deliver an incorrect or off-topic response, regardless of the LLM’s performance, as detailed in our article on RAG in production.

Impact on Quality, Latency and Reliability

A poor vector index may be acceptable at the prototype stage with a few thousand documents and a single user. However, once volumes reach several million vectors, latency must stay below a millisecond and access rights become more complex, the initial solution can become a bottleneck—impacting the performance of your applications.

For example, an industrial SME saw its internal RAG assistant’s latency rise to 500 ms with 200,000 indexed vectors, whereas the prototype ran under 50 ms. Switching to a clustered, distributed solution kept latency below 100 ms while integrating the confidentiality filters required by the IT department.

Choosing the right vector database from the project’s architecture phase means anticipating growth in volume, rights segmentation and concurrent load.

Selection Criteria and Types of Search

The choice of a vector database depends on technical and operational criteria: volume, latency, scalability, total cost of ownership and ecosystem maturity. There’s no one-size-fits-all solution, but rather a solution tailored to each business context.

Key Selection Criteria

Data volume (from thousands to billions of vectors) guides the choice between monolithic or distributed architectures, GPU or CPU. Target latency dictates the indexing technique (HNSW, IVF, DiskANN) and horizontal scalability.

The number of concurrent users, update frequency (streaming vs. batch), metadata filtering and degree of control (open source vs. managed service) affect total cost, operations and day-to-day management.

Security, document governance and compliance (GDPR, ISO standards) must be considered when selecting the solution and its hosting mode: public cloud, private cloud or on-premise.

Dense, Sparse and Hybrid Search

Dense search (vector search) finds content that is semantically close based on embedding distances. It’s ideal for concept matching, recommendation and similarity analysis.

Sparse search, based on keywords, remains crucial for named entities, product codes, contract numbers or domain-specific acronyms. It often relies on an integrated full-text engine.

Hybrid search combines both approaches to balance semantic coverage with keyword precision. Reranking, a second ranking step, typically uses a lightweight model to refine result relevance.

Metadata Filtering and Governance

In an internal application, you need to restrict query scope by language, country, department, document version or user role. This granularity ensures the AI only exposes what the user is authorized to see.

A private bank implemented asset-class and document-sensitivity filtering in its vector database, ensuring advisors access only authorized client data.

Therefore, the vector database design must align with document governance and rights management processes to guarantee technological sovereignty.

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Overview of Solutions and the Prototype Trap

Each vector solution addresses different needs: POC speed, managed production, self-hosted flexibility, distributed performance or R&D. To avoid the common prototype trap, you must plan your project’s trajectory.

Prototyping and POC

Chroma is often the first choice for experimentation: it can be set up in minutes, has a simple Python API and integrates with most embedding frameworks.

Pgvector in PostgreSQL offers a pragmatic lever for SMEs already using Postgres: relational data and vectors coexist without introducing a new database, as detailed in our guide on enterprise software.

At this stage, volume remains limited (a few hundred thousand vectors) and access rights are not very granular. Beyond that, performance and maintenance are quickly impacted.

Managed Production Solutions

Pinecone offers a managed service with low operational overhead, automatic scalability and stable performance. It’s ideal for quick delivery without infrastructure management.

Qdrant Cloud and Weaviate Cloud strike a balance between control and managed service: advanced filters, AI modules and deployment flexibility.

MongoDB Atlas Vector Search is a natural fit for teams already storing all their data in MongoDB. Vectors and documents coexist natively.

Advanced Performance and R&D

Milvus excels at high-volume workloads, distributed indexing and GPU acceleration. However, it requires Kubernetes and DevOps expertise to stabilize.

FAISS, a vector search library, remains a preferred choice for custom pipelines and R&D projects. It does not natively provide a server API, persistence or document governance.

Teams often pair FAISS with a custom orchestration layer for greater control, at the cost of increased engineering effort.

Use Cases, Digital Transformation and Edana Support

Vector databases are not just for chatbots: internal search engines, support assistants, tendering tools and recommendation systems all leverage the same building block. Every digital project should align with its business goals and maturity.

Diverse Uses Within Organizations

A major architecture firm uses a vector database to rapidly search its archives of plans and technical reports, reducing tender response preparation time by 40 %.

Digital Transformation and Innovation Levers

Beyond chatbots, a vector database can power a platform matching internal skills to projects or a personalized training recommendation engine based on employee profiles.

These initiatives are part of a broader digital transformation: consolidating silos, automating workflows and leveraging business data to gain agility and productivity.

Integrating with existing systems—ERP, electronic document management (EDM), CRM—is a key success factor for a sustainable, widely adopted solution.

Edana Support

Edana helps define the most suitable technology roadmap: choosing the vector database, cloud or on-premise architecture, CI/CD processes, monitoring and backups.

Our approach favors open source and scalability while minimizing vendor lock-in. We tailor the solution to your volumes, access policies, budgets and internal skills.

From initial audit to industrialization, our AI and infrastructure experts ensure a reliable, sustainable production rollout at an international scale.

Choosing the Right Foundation for Your Vector AI Systems

The choice of a vector database determines the performance, reliability and total cost of your AI system. It must be driven by the use case, expected volumes, security requirements and project roadmap, without over-architecting at the POC stage.

Our Edana experts are ready to assess your needs, select the most suitable solution and guide you through integration, ensuring your AI assistants, search engines and RAG tools rest on a solid, sustainable foundation.

Discuss your challenges with an Edana expert

By Benjamin

Digital expert

PUBLISHED BY

Benjamin Massa

Benjamin is an senior strategy consultant with 360° skills and a strong mastery of the digital markets across various industries. He advises our clients on strategic and operational matters and elaborates powerful tailor made solutions allowing enterprises and organizations to achieve their goals. Building the digital leaders of tomorrow is his day-to-day job.

FAQ

Frequently Asked Questions about Vector Databases

Which criterion should be prioritized when choosing a vector database for RAG?

The main criterion depends on your needs: expected volume, target latency, and filter complexity. For a few thousand vectors, an embedded solution or PostgreSQL with pgvector may suffice. Beyond 100,000 vectors and with sub-millisecond requirements, opt for a distributed (HNSW, IVF) or managed system with horizontal scalability to ensure performance and maintainability.

When should you move from a prototype to a distributed production solution?

It’s time to migrate as soon as latency breaches your SLAs or when volume and concurrent load increase. Concretely, if a POC struggles under 200,000 vectors or you need to enforce granular access controls, choose a clustered architecture. Anticipating this change prevents performance regressions and costly overhauls.

How does hybrid search improve result relevance?

Hybrid search combines embeddings (dense search) and keyword queries (sparse search) to merge semantic understanding with lexical precision. It retrieves semantically related documents while respecting exact entities like product codes or contracts. A final reranking with a lightweight model refines relevance and minimizes false positives.

What are the advantages of an open source solution versus a managed one?

Open source solutions offer full control, no vendor lock-in, and customization options. You manage the infrastructure while benefiting from predictable costs. Conversely, managed services (Pinecone, Qdrant Cloud) handle operations, guaranteeing automatic scalability, SLAs, and maintenance in exchange for operational costs and provider dependency.

How do you handle metadata filtering in a vector database?

Integrate metadata (language, country, user role) at indexing time to enable runtime filtering. Vector engines like Weaviate or Pinecone allow combining semantic queries with filter clauses. This approach ensures each user only accesses authorized documents, which is essential for GDPR compliance and internal governance.

Which indexing algorithms should you choose based on volume and latency?

For sub-millisecond latencies and a few million vectors, HNSW is recommended for its speed. For larger volumes or optimized disk access, IVF or DiskANN reduces memory footprint. GPU clusters (Milvus) deliver excellent performance on billions of vectors in parallel, at the cost of increased operational complexity.

What are common mistakes when integrating a vector database?

Common mistakes include starting a POC without planning for scale, neglecting monitoring and access governance, or choosing a service unsuitable for future volumes. Omitting reranking or hybrid search can also reduce relevance. Plan for data growth, security, and operational costs from the outset.

How do you measure the performance and KPIs of a vector database?

Track average latency and 95th percentile of queries, recall and precision rates. Also measure throughput, CPU/GPU usage, and total cost of ownership over time. Include monitoring of errors and applied filters to ensure reliability and SLA compliance.

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