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GenAI For Practitioners

Best Vector DBs for Retrieval-Augmented Generation (RAG)

Kristen Kehrer
Kristen Kehrer

Data Evangelist

8 min read Dec 18, 2023


Generative AI is on the brink of transforming diverse sectors, promising trillions of dollars in value across applications such as customer operations, marketing and sales, and research and development (R&D). As Gen AI increasingly becomes incorporated into business operations, the scalability of fundamental components becomes essential for sustainable success. The vector database is crucial among these components, providing critical support for the various Gen AI use cases organizations are set to develop.

Retrieval-Augmented Generation (RAG)
Retrieval-Augmented Generation (RAG)

With the demand for LLM-enhanced applications increasing rapidly, Retrieval-Augmented Generation (RAG) models have become essential tools. They combine retrieval and generation tasks to enrich contextual understanding and synthesize information. The importance of vector databases has become increasingly prominent in RAG, as they form the foundation for the retrieval process, enhancing the efficiency and accuracy of RAG models.

This article explores vector DBs and their role in RAG and highlights the top vector databases suitable for RAG.
Understanding Vector Databases
A vector database efficiently stores, manages, and indexes vast quantities of high-dimensional vector data. These databases are gaining popularity due to their ability to enhance Gen AI use cases.


Retrieval-Augmented Generation (RAG)
Source: Analytics Vidhya

Vector databases play a crucial role in storing and querying high-dimensional data for AI and machine learning applications, a trend expected to persist with increasing adoption. Unlike traditional databases organized in rows and columns, a vector database represents data points using fixed-dimensional vectors clustered based on similarity. This design is well-suited for RAG use cases and applications due to its ability to perform swift and low-latency queries, especially when used as a powerful similarity search engine for high-dimensional data.

Key Features of Vector Databases

Here is a list of a few key features of vector DBs.

Efficient Storage and Retrieval: Vector databases excel in efficiently storing and retrieving high-dimensional data. Their design prioritizes quick access to vectors, ensuring optimal performance for AI and machine learning tasks.

Scalability: A crucial feature of vector databases is their scalability. Applications with evolving requirements and increasing amounts of vector data can seamlessly scale using these tools.

Query Performance: Vector databases optimize query speed for real-time applications, excelling in swift access and processing of vector information. Its exceptional capability in performing similarity searches enhances overall query performance for precise matching in AI and ML tasks.

Dimensional Flexibility: Vector databases offer dimensional flexibility, with each vector having a variable number of dimensions, ranging from tens to thousands. However, in RAG use cases, consistency is maintained by keeping a fixed dimensionality. Different dimension counts may indicate distinct RAG applications.

Integration with AI and ML Frameworks: Many vector databases seamlessly integrate with popular AI and machine learning frameworks, simplifying the deployment and utilization of vector data within these environments.

Security and Access Control: Vector databases often come equipped with robust access control mechanisms and security features to ensure data integrity and security.

The Role of Vector Databases in RAGs

Vector databases play a crucial role in Retrieval-Augmented Generation (RAG) for generative AI workflows. RAG, preferred by enterprises for its swift time-to-market and reliable outputs in areas like customer care and HR/Talent, relies on high-dimensional vector data.

During inference, vector databases excel at efficiently storing, indexing, and retrieving documents, ensuring the speed, precision, and scale essential for applications like recommendation engines and chatbots.

Vector databases play a critical role in enhancing the efficiency of Retrieval-Augmented Generation (RAG) for long-term memory in Large Language Models (LLMs). For instance, integrating specific data into general-purpose models like IBM watsonx.ai’s Granite via a vector database refines understanding and enhances performance in diverse AI applications.

Top Vector Databases for RAGs

In RAG, the strategic selection of vector databases is crucial for efficient data management. Here, we will explore and analyze the leading vector DBs that enhance the capabilities of organizations handling complex relational data.

1. Milvus
Milvus is an open-source, highly scalable vector database designed for efficient similarity search. With advanced indexing algorithms, Milvus handles massive embedding vectors generated by machine learning models, providing blazing-fast retrieval speeds. It is easy to use, highly available, and cloud-native, making it a versatile choice for large-scale vector data applications.

Milvus Workflow
Milvus Workflow

Key Features

  • Advanced indexing algorithms for handling massive embedding vectors from machine learning models.
  • Intuitive SDKs for quick creation of large-scale similarity search services.
  • Battle-tested high availability and resilience in various enterprise use cases.
  • Cloud-native architecture, separating compute from storage for flexible scaling.
  • Support for various data types, UDF support, enhanced vector search, and more.

2. Pinecone
Pinecone is a highly trusted vector database that is frequently used for AI projects. With Pinecone, users can create an index in just 30 seconds and perform ultra-fast vector searches for search, recommendation, and detection applications. It supports billions of embeddings, providing more relevant results through metadata filtering and real-time updates.

Pinecone Architecture
Pinecone Architecture

Key Features

  • Real-time updates keep the Pinecone index fresh as data changes.
  • Implements hybrid search by combining vector search with keyword boosting.
  • SOC 2 and HIPAA compliant for data security and control.
  • Reliable support for mission-critical applications backed by SLAs and observability.
  • Fully cloud-native and managed, available on AWS, Azure, GCP, and marketplaces of your choice.

3. Weaviate
Weaviate, an open-source, AI-native vector database, is the ultimate solution for developers seeking simplicity and reliability in building and scaling AI applications. With a focus on hybrid search, secure RAG-building, and generative feedback loops, Weaviate empowers developers of all levels. Its pluggable ML models, scalable multi-tenant architecture, and flexible deployment options ensure seamless integration into diverse business environments.

Weaviate Architecture
Weaviate Architecture

Key Features

  • Enhances AI app reliability, reduces AI hallucinations, and ensures security.
  • Automatically improves data quality using content generated by LLMs.
  • Native multi-tenancy, data compression, and filtering for confident scaling.
  • Adaptable to business needs‚ÄĒruns as open source, managed service, or within VPC.
  • Support for bringing your own vectors or choosing modules with out-of-the-box support for vectorization.

4. Elasticsearch
Elasticsearch offers an efficient solution for creating, storing, and searching vector embeddings at scale. With a focus on hybrid retrieval, Elasticsearch seamlessly combines text and vector search capabilities for superior relevance and accuracy. Its comprehensive vector database includes various retrieval types, machine learning model architectures, and robust search experience-building tools.

Elasticsearch Architecture
Elasticsearch Architecture

Key Features

  • Combine text and vector search for optimal relevance and accuracy.
  • Elasticsearch includes a complete vector database, supporting text, sparse and dense vectors, and hybrid retrieval.
  • Capture meaning, context, and associations with the flexibility to pick embedding models.
  • Assign granular role-based access controls with document and field-level security.
  • Leverage filters and faceting capabilities for refined vector search.

5. Vespa
Vespa, the AI-driven online vector database, offers unbeatable performance at any scale. Used by industry leaders like Spotify and Yahoo, Vespa is a fully featured search engine and vector database supporting vector, lexical, and structured data searches. Its integrated machine-learned model inference enables real-time AI application, making it the ideal platform for recommendation, personalization, conversational AI, and semi-structured navigation.

Vespa Architecture
Vespa Architecture

Key Features

  • Supports vector search (ANN), lexical search, and structured data search in the same query.
  • Proven scaling and high availability for production-ready search applications.
  • Ideal platform for large language models, offering real-time vector and text data storage and search capabilities.
  • Supports e-commerce applications with structured navigation, combining search, recommendation, and structured data.
  • Automatic distribution and redistribution of data, eliminating concerns about data division and distribution.

The table below contains the pros and cons and supported indexes of vector databases discussed above.

Vector DBs Pros Cons Supported Indexes
Milvus Flexible data handling, fast vector similarity search, scalability, and high availability.  Learning curve. Milvus Lite may not be a good option for high-performance projects. FLAT, IVF_FLAT, IVF_PQ, HNSW, RHNSW_FLAT, RHNSW_PQ, RHNSW_SQ, and, ANNOY.
Pinecone Easy to use, scalable, flexible, high-performance vector DB. Expensive to use, limitations for organizations preferring on-premise solutions. Proprietary composite index.
Weaviate Fast, filtered, and semantic search from end to end. 
Scales to billion objects, backup, and storage capabilities.
Learning curve. 
Unknown cost implications for fully managed offerings.
Elasticsearch Document-oriented NoSQL database.
Schemeless and real-time search and analytics. Scalable architecture.
High admin overhead. 
Query speed decreases as index size increases
¬†Lucene’s HNSW
VespaMilvus Enterprise-ready hybrid search. 
Accurate and fast.
Highly scalable.
Learning curve for new users. 
Configuration complexity.


As Retrieval-Augmented Generation (RAG) models become more prevalent in generative AI, the importance of vector databases becomes crucial. They’re essential because they’re good at storing data, can handle a lot, work well for searching, and seamlessly integrate with other components.

Choosing a suitable vector database is essential in RAG. Milvus, Pinecone, Weaviate, Elasticsearch, and Vespa each have their strengths and weaknesses, but they all help manage data well for generative AI.

Using vector databases can significantly enhance the efficiency and accuracy of RAG systems\applications. They can also manage more significant tasks, such as searching for similar items or combining various searches. For businesses venturing into generative AI, selecting the appropriate vector database is crucial.

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