Retrieval-Augmented Generation (RAG): Core Architecture

MEDIUM8 min readby AdminJune 19, 2026History
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Master the architectural RAG pipeline: document chunking, embedding, vector storage, context injection, and generation.

#ai-engineering#rag#embeddings#vector-db#interview-prep

The RAG Pipeline

Retrieval-Augmented Generation (RAG) updates LLMs with external, dynamic knowledge without needing expensive parameter training. The architecture runs in three stages:

  1. Ingestion: Loading enterprise documents, splitting them into logical chunks (e.g. 500 characters with 50-character overlap), and translating text to high-dimensional mathematical vector embeddings.
  2. Retrieval: When a user asks a question, the question is vectorized, and a vector database performs a similarity search to fetch the top-k most relevant chunks.
  3. Generation: The fetched text chunks are injected into the prompt context alongside the user query. The LLM references this context to generate a highly accurate, grounded answer.

RAG Pipeline System flow

[User Query] ---> [Embedding Model] ---> [Query Vector]
                                                |
                                                v
[LLM Generation] <--- [Prompt Context] <--- [Vector Database Search]
        |                 (Query + Chunks)
        v
[Grounded Response]

Chunking Strategies & Overlaps

Example

When dividing documents, chunk sizes must be balanced. Chunks that are too small lack context, while chunks that are too large dilute semantic focus. • Recursive Character Chunking splits text dynamically by a list of separators (like paragraphs, newlines, and spaces), keeping sentences intact. • Chunk Overlap (e.g., 10%) ensures context continuity between boundary lines.

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