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Hexagonal Architecture for Provider-Agnostic RAG Pipelines

A developer built a provider-agnostic RAG pipeline using hexagonal architecture, decoupling the application from specific LLMs, vector databases, and document-processing frameworks through lazy imports and abstract interfaces. The demo stack combines LangChain, llama.cpp, Mistral.ai, Qwen embeddings, PostgreSQL with pgvector, and Telegraf/Prometheus observability on Docker, with the full implementation published on GitHub as yoga1290/rag.

by read1 min views2 publishedSep 25, 2026

Demo stack: LangChain, Llama.cpp, Mistral.ai, Qwen Embeddings, PostgreSQL, Telegraf, Prometheus on Docker.

I recently came across Machine Learning Mastery's guide on Building a RAG Pipeline with llama.cpp and decided to try it myself.

One thing quickly became apparent: some of the APIs and methods used in the example had already changed or become deprecated.

That led me to a bigger question:

How do you design a RAG system that can evolve as the underlying technologies change?

Instead of tightly coupling the application to a specific LLM, vector database, or document-processing framework, I experimented with a more modular architecture.

This way I get a more resilient architecture, for instance if I need a transition between local on-premise to fully on cloud or just hybrid; ability to switch to different database like PostgreSQL instead of ChromaDB, due to the data integration and ACID compliance!

A few principles became particularly important:

def importOnCall(..):
    from.. import .. # Lazy import
    return ResultModel(..) # tied to Abstracts & Models
vectorstore: VectorStore = PGVectorStore(...)
vectorstore: VectorStore = OtherVectorDBService(..)

🛠️ Separation of responsibilities

Each layer has a focused responsibility:

📦️ Observability, Containerization & Resource/Network monitoring, Confiurations are pass in form of Environment Variables, see sample.env. Telegraf is used to monitor the resource consumsion and network traffic, and project metrics to Prometheus. See the 👁️ Observability section.

The complete implementation is available on GitHub: yoga1290/rag

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