Build RAG Chatbot with LangChain, pgvector, AWS Bedrock Claude 3.5 Haiku, and voyage-code-2

Introduction to RAG

Retrieval-Augmented Generation (RAG) is a game-changer for GenAI applications, especially in conversational AI. It combines the power of pre-trained large language models (LLMs) like OpenAI’s GPT with external knowledge sources stored in vector databases such as Milvus and Zilliz Cloud, allowing for more accurate, contextually relevant, and up-to-date response generation. A RAG pipeline usually consists of four basic components: a vector database, an embedding model, an LLM, and a framework.

Key Components We'll Use for This RAG Chatbot

This tutorial shows you how to build a simple RAG chatbot in Python using the following components:

LangChain: An open-source framework that helps you orchestrate the interaction between LLMs, vector stores, embedding models, etc, making it easier to integrate a RAG pipeline.
Pgvector: an open-source extension for PostgreSQL that enables efficient storage and querying of high-dimensional vector data, essential for machine learning and AI applications. Designed to handle embeddings, it supports fast approximate nearest neighbor (ANN) searches using algorithms like HNSW and IVFFlat. Since it is just a vector search add-on to traditional search rather than a purpose-built vector database, it lacks scalability and availability and many other advanced features required by enterprise-level applications. Therefore, if you prefer a much more scalable solution or hate to manage your own infrastructure, we recommend using Zilliz Cloud, which is a fully managed vector database service built on the open-source Milvus and offers a free tier supporting up to 1 million vectors.)
AWS Bedrock Claude 3.5 Haiku: An advanced model from Anthropic, Claude 3.5 is designed for scalable natural language processing within AWS Bedrock. It offers enhanced reasoning and contextual understanding, making it well-suited for applications such as conversational agents, content generation, and data analysis, delivering both speed and accuracy in enterprise settings.
Voyage Code 2: This AI model specializes in code generation and programming assistance, designed to enhance developer productivity. It offers robust support in writing, debugging, and optimizing code across various languages. Ideal for software development projects, it streamlines coding workflows and facilitates rapid prototyping and learning for both novice and experienced programmers.

By the end of this tutorial, you’ll have a functional chatbot capable of answering questions based on a custom knowledge base.

Note: Since we may use proprietary models in our tutorials, make sure you have the required API key beforehand.

Step 1: Install and Set Up LangChain

%pip install --quiet --upgrade langchain-text-splitters langchain-community langgraph

Step 2: Install and Set Up AWS Bedrock Claude 3.5 Haiku

pip install -qU "langchain[aws]"

# Ensure your AWS credentials are configured

from langchain.chat_models import init_chat_model

llm = init_chat_model("anthropic.claude-3-5-haiku-20241022-v1:0", model_provider="bedrock_converse")

Step 3: Install and Set Up voyage-code-2

pip install -qU langchain-voyageai

import getpass
import os

if not os.environ.get("VOYAGE_API_KEY"):
  os.environ["VOYAGE_API_KEY"] = getpass.getpass("Enter API key for Voyage AI: ")

from langchain-voyageai import VoyageAIEmbeddings

embeddings = VoyageAIEmbeddings(model="voyage-code-2")

Step 4: Install and Set Up pgvector

pip install -qU langchain-postgres

from langchain_postgres import PGVector

vector_store = PGVector(
    embeddings=embeddings,
    collection_name="my_docs",
    connection="postgresql+psycopg://...",
)

Step 5: Build a RAG Chatbot

Now that you’ve set up all components, let’s start to build a simple chatbot. We’ll use the Milvus introduction doc as a private knowledge base. You can replace it with your own dataset to customize your RAG chatbot.

import bs4
from langchain import hub
from langchain_community.document_loaders import WebBaseLoader
from langchain_core.documents import Document
from langchain_text_splitters import RecursiveCharacterTextSplitter
from langgraph.graph import START, StateGraph
from typing_extensions import List, TypedDict

# Load and chunk contents of the blog
loader = WebBaseLoader(
    web_paths=("https://milvus.io/docs/overview.md",),
    bs_kwargs=dict(
        parse_only=bs4.SoupStrainer(
            class_=("doc-style doc-post-content")
        )
    ),
)

docs = loader.load()

text_splitter = RecursiveCharacterTextSplitter(chunk_size=1000, chunk_overlap=200)
all_splits = text_splitter.split_documents(docs)

# Index chunks
_ = vector_store.add_documents(documents=all_splits)

# Define prompt for question-answering
prompt = hub.pull("rlm/rag-prompt")


# Define state for application
class State(TypedDict):
    question: str
    context: List[Document]
    answer: str


# Define application steps
def retrieve(state: State):
    retrieved_docs = vector_store.similarity_search(state["question"])
    return {"context": retrieved_docs}


def generate(state: State):
    docs_content = "\n\n".join(doc.page_content for doc in state["context"])
    messages = prompt.invoke({"question": state["question"], "context": docs_content})
    response = llm.invoke(messages)
    return {"answer": response.content}


# Compile application and test
graph_builder = StateGraph(State).add_sequence([retrieve, generate])
graph_builder.add_edge(START, "retrieve")
graph = graph_builder.compile()

Test the Chatbot

Yeah! You've built your own chatbot. Let's ask the chatbot a question.

response = graph.invoke({"question": "What data types does Milvus support?"})
print(response["answer"])

Example Output

Milvus supports various data types including sparse vectors, binary vectors, JSON, and arrays. Additionally, it handles common numerical and character types, making it versatile for different data modeling needs. This allows users to manage unstructured or multi-modal data efficiently.

Optimization Tips

As you build your RAG system, optimization is key to ensuring peak performance and efficiency. While setting up the components is an essential first step, fine-tuning each one will help you create a solution that works even better and scales seamlessly. In this section, we’ll share some practical tips for optimizing all these components, giving you the edge to build smarter, faster, and more responsive RAG applications.

LangChain optimization tips

To optimize LangChain, focus on minimizing redundant operations in your workflow by structuring your chains and agents efficiently. Use caching to avoid repeated computations, speeding up your system, and experiment with modular design to ensure that components like models or databases can be easily swapped out. This will provide both flexibility and efficiency, allowing you to quickly scale your system without unnecessary delays or complications.

pgvector optimization tips

To optimize pgvector in a Retrieval-Augmented Generation (RAG) setup, consider indexing your vectors using GiST or IVFFlat to significantly speed up search queries and improve retrieval performance. Make sure to leverage parallelization for query execution, allowing multiple queries to be processed simultaneously, especially for large datasets. Optimize memory usage by tuning the vector storage size and using compressed embeddings where possible. To further enhance query speed, implement pre-filtering techniques to narrow down search space before querying. Regularly rebuild indexes to ensure they are up to date with any new data. Fine-tune vectorization models to reduce dimensionality without sacrificing accuracy, thus improving both storage efficiency and retrieval times. Finally, manage resource allocation carefully, utilizing horizontal scaling for larger datasets and offloading intensive operations to dedicated processing units to maintain responsiveness during high-traffic periods.

AWS Bedrock Claude 3.5 Haiku optimization tips

Claude 3.5 Haiku on AWS Bedrock is an optimized version of Haiku with improved efficiency and response quality. Enhance performance by using high-precision vector embeddings and filtering irrelevant data before retrieval. Keep prompts brief yet structured to improve clarity and token efficiency. Adjust temperature between 0.1 and 0.3 to balance accuracy and variation. Utilize AWS Bedrock’s low-latency infrastructure to maintain responsiveness in real-time applications. Implement API request batching for large-scale workloads and cache frequent queries to optimize cost and performance. When deploying multiple models, use Haiku for fast responses while reserving larger models for deep analytical tasks.

voyage-code-2 optimization tips

voyage-code-2 provides solid performance for code-related RAG tasks but requires careful retrieval optimization to ensure efficient and accurate results. Use structured embeddings to improve code snippet search and retrieval precision. Format prompts with clear structure, including specific instructions, function signatures, and constraints, to enhance output quality. Keep temperature low (0.1–0.2) for accuracy in deterministic tasks while allowing slight variation for exploratory coding tasks. Enable caching for frequently requested programming patterns to optimize efficiency. Use parallelized execution and request batching to handle large-scale queries effectively. In multi-model deployments, assign voyage-code-2 to standard code completion tasks while leveraging more advanced models for deeper analysis and architectural recommendations.

By implementing these tips across your components, you'll be able to enhance the performance and functionality of your RAG system, ensuring it’s optimized for both speed and accuracy. Keep testing, iterating, and refining your setup to stay ahead in the ever-evolving world of AI development.

RAG Cost Calculator: A Free Tool to Calculate Your Cost in Seconds

Estimating the cost of a Retrieval-Augmented Generation (RAG) pipeline involves analyzing expenses across vector storage, compute resources, and API usage. Key cost drivers include vector database queries, embedding generation, and LLM inference.

RAG Cost Calculator is a free tool that quickly estimates the cost of building a RAG pipeline, including chunking, embedding, vector storage/search, and LLM generation. It also helps you identify cost-saving opportunities and achieve up to 10x cost reduction on vector databases with the serverless option.

Calculate your RAG cost now.

Calculate your RAG cost

What Have You Learned?

By diving into this tutorial, you’ve unlocked the power of combining cutting-edge tools to build a RAG system that’s both intelligent and efficient! You learned how LangChain acts as the glue, seamlessly connecting your data pipeline, retrieval logic, and generative AI. By integrating pgvector as your vector database, you saw firsthand how to store and query embeddings at scale, turning unstructured data into searchable knowledge. Then came the magic of AWS Bedrock’s Claude 3.5 Haiku—the LLM that brings speed and precision to generating human-like responses—paired with voyage-code-2 embeddings, which transform text into rich numerical representations, ensuring your system understands context and nuance. Together, these components create a dynamic pipeline where retrieval meets generation, empowering your app to deliver accurate, context-aware answers every time.

But this tutorial didn’t stop at the basics! You discovered pro tips like optimizing chunking strategies for better retrieval, tuning pgvector indexes for speed, and even using the free RAG cost calculator to estimate expenses and scale wisely. Now you’re equipped to balance performance, cost, and user experience like a pro. Imagine the possibilities: chatbots that truly understand your users, search engines that surface hidden insights, or personalized content generators that feel almost human. The tools are in your hands, and the future of AI-driven applications is yours to shape. So go ahead—experiment, tweak, and innovate! Start building smarter RAG systems today, and watch your ideas come to life with the same excitement and confidence you’ve gained here. The next breakthrough is just a line of code away. 🚀

Further Resources

🌟 In addition to this RAG tutorial, unleash your full potential with these incredible resources to level up your RAG skills.

How to Build a Multimodal RAG | Documentation
How to Enhance the Performance of Your RAG Pipeline
Graph RAG with Milvus | Documentation
How to Evaluate RAG Applications - Zilliz Learn
Generative AI Resource Hub | Zilliz

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