EP230: RAG vs Agentic RAG

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This week’s system design refresher:

• Top 5 AI Building Blocks Every Engineer Should Know (Youtube Video)

• RAG vs Agentic RAG

• OAuth (authorization) + OIDC (authentication layer)

• Understanding the Linux Directory Structure

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Top 5 AI Building Blocks Every Engineer Should Know

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RAG vs Agentic RAG

RAG is a technique that combines information retrieval with an LLM to generate answers. Here is how RAG works at a high level:

• A user asks a question to the application.

• The retrieval system fetches the relevant information from a knowledge base.

• The application adds that information to the prompt.

• The LLM uses that context to generate an answer.

RAG usually follows a predefined retrieval process. The quality of its results depends on the accuracy of the retrieved context.

Agentic RAG follows a different approach. Instead of retrieving once, an agent can repeatedly fetch and evaluate information until it has enough evidence to generate an answer. Here is how it typically works:

• An agent selects the right tools based on the task.

• Those tools can search documents, APIs, databases, or the web.

• The fetched evidence is then checked if it is sufficient for the task.

• If it is not, the agent can adjust its search or choose a different tool.

• Once sufficient evidence is achieved, LLM uses that context to generate an answer.

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OAuth (authorization) + OIDC (authentication layer)

If you want to show Google Calendar events inside your Slack channel, it will require permission to read your calendar. How would you let Slack access your calendar without giving Slack your Google password?

This is where OAuth 2.0 comes into the picture. Slack basically never sees your Google password. It lets an app access a protected resource on your behalf without knowing your credentials.

Basically OAuth 2.0 handles authorization. In Slack’s case, it will send you to Google’s authorization server, where you will login and give Slack permission to access your calendar. Google gives you the authorization code, and Slack will exchange that code for access_token.

If Slack also wants to authenticate the identity of the person requesting the access to Google Calendar, you will need OIDC for that. The OIDC handles authentication and sits on top of OAuth 2.0.

OAuth answers what you’re allowed to touch, while OIDC answers who you are. In addition to the access_token returned by the authorization server, this time, it will also send an id_token, a signed JWT which basically tells Slack who just signed in.

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Understanding the Linux Directory Structure

The linux directory structure starts with the root directory "/". Let’s navigate to the directory structure of linux.

The kernel image and bootloader files are stored in the "boot" directory. Your hard disk partitions and device related files are located in the “dev” directory.

All your programs and libraries are stored in "bin", "sbin", "usr", and "lib" directories. Like, your installed software is located in the "usr" directory. Ever wondered where ls, cp, and cat commands are? "bin" is the directory that holds those essential commands.

System-wide configuration goes in "etc", and "var" holds data that changes as the system runs, which is where you'll find your logs.

If you have a USB drive, it gets mounted in “bin” folder. For any external drive that you want to mount temporarily on your linux machine, "media" is the directory for it. If you have multiple user accounts, "home" is the directory for each user in your linux system.