RAG, Fine-tuning, and Prompting: What is what and how to choose the right approach for your LLM Applications
PS: I made this whole article about dating. It's fun and good way to learn through examples
When preparing for a date, you want to nail three things:
Knowing what to say (Prompting).
Knowing the right details about your date (RAG).
Adapting your approach to match their personality (Fine-tuning).
But let’s address the obvious question: why can’t you just rely on your natural charm—or, in LLM terms, the base model?
Why the Base Model Isn’t Enough
The base model of you is like showing up to a date thinking, I’ve got this. Sure, you’re smart and charming, but you’re also clueless about the specifics of this particular person. What if they love coffee but hate ice cream, and you suggest a dessert spot? That’s an instant flop.
LLMs are the same. They’re trained on a ton of general data—books, websites, articles—but they don’t know everything. They’re broad but shallow, lack context, and come off generic. If you want to impress your date (or handle specific tasks with an LLM), you need tools like Prompting, RAG, and Fine-tuning to step up your game.
Prompting: The Clever Pickup Line
Prompting is like having a solid icebreaker ready. It’s quick, easy, and works when you don’t need to dive too deep.
For example, you might start with: "What’s a book that totally changed your perspective?"
It’s a great way to spark conversation without knowing their specific tastes.
With LLMs, prompting is like giving the model clear instructions in real time: “Answer this question in a friendly, lighthearted tone.” It’s perfect for simple, predictable tasks, but just like a one-liner won’t carry a whole date, prompting alone can’t handle complex or nuanced situations.
RAG: Doing Your Homework
RAG (Retrieval-Augmented Generation) is like doing some light stalking before the date (the good kind, obviously :D). You check their profile, learn they love sushi and live in Chennai, and show up ready with: "Have you tried Nasi and Mee Sushi? I heard their dragon roll is amazing!"
This shows you’ve made an effort, and it gives the conversation a personal touch.
For LLMs, RAG is like giving them access to a database of up-to-date, specific information. It’s the solution when the base model doesn’t have niche knowledge or needs to handle real-time queries. Like prepping for a date, RAG ensures the model can retrieve the right info when it matters.
Fine-tuning: Becoming the Dream Date
Fine-tuning is where you completely adapt your vibe to match your date’s energy. If they love deep conversations, you don’t hit them with,
Hybrid: The Best of Both Worlds
Sometimes, you need both preparation (RAG) and adaptability (Fine-tuning). Imagine your date loves books and sushi. You’ve done your homework (RAG) and found the perfect spot like Nasi and Mee Sushi. Then, during the date, you match their vibe (Fine-tuning) by saying:
The Base Model Isn’t the Final Destination
A date—or a well-built LLM application—needs more than just the basics. The base model might get you started, but if you really want to make an impression:
Use Prompting for quick, simple tasks.
Use RAG when you need specific, external knowledge.
Use Fine-tuning to align tone and behavior.
Combine them for maximum impact when the situation calls for both precision and personality.
Takeaways
The base model is like you before a date—smart but unprepared. If you want to succeed, you need the right tools to tailor your approach. Just like in dating, success comes from effort, understanding, and knowing when to use the right strategy.
Sanjay - so good to hear from you and love this stack. Keep up the great work.