LLM Apps in Production (RAG + Vector DB + Caching) · Lesson

Building a Simple RAG Pipeline

Implement a basic RAG workflow from data ingestion to generating responses using a chosen LLM.

Building a Simple RAG Pipeline is a free LLM Apps in Production (RAG + Vector DB + Caching) lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the LLM Apps in Production (RAG + Vector DB + Caching) learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Intro to RAG Pipelines

You've learned what RAG is and why it's powerful. Now, let's build one! A Retrieval Augmented Generation (RAG) pipeline is a sequence of steps that combine an LLM with external data.

Its main goal is to give LLMs up-to-date, factual information, reducing "hallucinations" and improving response quality.

Understanding the RAG Flow

Think of a RAG pipeline as having two main phases: preparation and querying. First, you get your data ready. Then, when a user asks a question, your system finds relevant info and uses it to help the LLM answer.

Preparation: Ingest & Index Data
Querying: Retrieve & Generate Response

Step 1: Prepare Your Knowledge Base

Before an LLM can use your data, it needs to be processed. This involves:

Loading: Getting data from various sources (PDFs, websites, databases).
Chunking: Breaking large documents into smaller, manageable pieces (chunks). A chunk might be a few sentences or a paragraph.

Smaller chunks are easier to search and fit into an LLM's context window.

Step 2: Turn Chunks into Embeddings

How do we "search" text semantically? We turn it into numbers! An embedding model converts each text chunk into a list of numbers called a vector embedding.

These vectors capture the meaning of the text. Chunks with similar meanings will have vectors that are "close" to each other in a mathematical sense.

Step 3: Store for Fast Retrieval

Once you have vector embeddings for all your chunks, you need to store them efficiently. A vector store (or vector database) is specialized for this.

It allows for very fast "similarity search" – finding vectors that are closest to a given query vector. This is key for quickly retrieving relevant information.

Processing a User Query

When a user types a question, your RAG pipeline springs into action. The first thing that happens is that the user's query itself is converted into a vector embedding.

This query embedding will then be used to search your stored data for relevant information.

Step 4: Find the Best Matches

With the user query's embedding, the RAG system performs a similarity search in your vector store. It looks for data chunks whose embeddings are most similar to the query's embedding.

The most similar chunks are considered the most relevant "context" for answering the user's question.

Step 5: Enhance the LLM's Prompt

Now, we combine the user's original question with the retrieved context. This creates an augmented prompt.

Instead of just asking, "What is X?", the prompt becomes something like: "Given this information: [retrieved chunks], what is X?"

This guides the LLM to use the provided facts.

Step 6: LLM Generates the Answer

Finally, the augmented prompt is sent to the Large Language Model. The LLM processes both the user's question and the retrieved context.

It then generates a response that is grounded in the factual information provided by your data, rather than relying solely on its pre-trained knowledge.

Visualize the RAG Steps

Here's a conceptual Python example showing the flow. Imagine load_data, chunk_text, create_embeddings, index_embeddings, search_vector_store, and generate_llm_response are functions you'd implement.

Try running this example to see the sequence!

public class Main {
  public static void main(String[] args) {
    System.out.println("1. User query received: What is RAG?");

    // Simulate embedding the query
    String queryEmbedding = "Embedding for 'What is RAG?'";
    System.out.println("2. Query embedded: " + queryEmbedding);

    // Simulate retrieving relevant chunks from a vector store
    String[] retrievedChunks = {
      "Chunk 1: RAG helps LLMs use external facts.",
      "Chunk 2: Vector databases store embeddings."
    };
    System.out.println("3. Retrieved relevant chunks: " + String.join(", ", retrievedChunks));

    // Simulate augmenting the LLM prompt
    String augmentedPrompt = (
      "Based on the following context:\n"
      + String.join(" ", retrievedChunks) + "\n\n"
      + "Answer the question: What is RAG?"
    );
    System.out.println("4. Augmented LLM prompt created.");

    // Simulate LLM response generation
    String llmResponse = (
      "RAG pipelines enhance LLMs by providing external, "
      + "factual context from stored documents, which helps "
      + "reduce hallucinations and improve accuracy."
    );
    System.out.println("5. LLM generated response.");

    System.out.println("\nFinal Answer: " + llmResponse);
  }
}

RAG Pipeline Quiz

Which of the following accurately describes the correct order of steps when a user submits a query in a RAG pipeline?

Recap: Building RAG

Great job! You've now grasped the full flow of a basic RAG pipeline. We covered:

The preparation steps: ingesting, chunking, embedding, and indexing your data.
The querying steps: embedding the user query, retrieving context, augmenting the prompt, and generating a response with the LLM.

This foundational understanding will help you build more robust LLM applications!

Frequently asked questions

Is the “Building a Simple RAG Pipeline” lesson free?

Yes — the full text of “Building a Simple RAG Pipeline” is free to read here on the web, and the LLM Apps in Production (RAG + Vector DB + Caching) course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the LLM Apps in Production (RAG + Vector DB + Caching) course, upgrade to CoddyKit PRO.

What will I learn in “Building a Simple RAG Pipeline”?

Implement a basic RAG workflow from data ingestion to generating responses using a chosen LLM. You practise LLM Apps in Production (RAG + Vector DB + Caching) with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start LLM Apps in Production (RAG + Vector DB + Caching)?

No prior experience is required. LLM Apps in Production (RAG + Vector DB + Caching) on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Building a Simple RAG Pipeline” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this LLM Apps in Production (RAG + Vector DB + Caching) lesson?

Yes. Every LLM Apps in Production (RAG + Vector DB + Caching) lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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