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AI systemsPro

Build retrieval systems you can measure.

Building RAG Systems & Vector Search

Move from keyword search to dense and hybrid retrieval, chunking, reranking, HyDE, ANN indexes, and rigorous ranking evaluation.

What you will be able to do

Leave with capability, not just vocabulary.

Build lexical, dense, and hybrid retrieval

Choose chunking and diversification strategies

Add reranking and query transformation

Evaluate retrieval with Recall@k, MRR, and nDCG

Running example

Helpwell, a customer-support knowledge corpus whose retrieval quality is measured before and after every technique.

Prerequisites

Basic Python and a high-level understanding of LLM applications are helpful.

Curriculum

Every module earns the next one.

Open any module to review its exact sections. Progress and completion follow you through the course.

8 modules · ~9 hours
01
Module 1

The Retrieval Problem

BeginnerFree preview

Topics include RAG vs fine-tune vs long-context, Lost in the middle, Chunking, and more.

View 5 sections
  1. 1RAG vs Fine-Tuning vs Long-Context: Answers to Different Questions
  2. 2Lost in the Middle: Why a Bigger Window Isn't a Free Retriever
  3. 3Chunking: Deciding the Unit of Recall
  4. 4Keyword Search From Scratch: TF-IDF, Then the Two Fixes That Make BM25
  5. 5The Gold Set: You Can't Improve What You Don't Measure
70 min5 sections
Open module
02
Module 2

Embeddings as Retrieval Geometry

IntermediatePro

Topics include Vector space, Cosine vs dot, Normalization, and more.

View 5 sections
  1. 1From Words to Vectors: What an Embedding Actually Encodes
  2. 2Measuring Closeness: Cosine, Dot Product, and Normalization
  3. 3Brute-Force kNN: Your First Dense Retriever
  4. 4The Curse of Dimensionality: Why High-D Similarity Is Weird
  5. 5Dense vs Keyword: Shipping AskHelpwell v1
70 min5 sections
Open module
03
Module 3

Chunking & Metadata

IntermediatePro

Topics include Fixed/recursive/semantic chunking, Overlap, Chunk size, and more.

View 5 sections
  1. 1You Retrieve Chunks, Not Documents
  2. 2Fixed, Recursive, and Semantic Splitting
  3. 3Chunk Size: The Precision vs Context Tradeoff
  4. 4Metadata Filtering: Version, Area, and Freshness
  5. 5Re-Chunking AskHelpwell
65 min5 sections
Open module
04
Module 4

Hybrid Search & Fusion

IntermediatePro

Topics include When dense fails, Reciprocal Rank Fusion, Weighted hybrid, and more.

View 5 sections
  1. 1Two Witnesses: Where Each Retriever Wins and Loses
  2. 2Reciprocal Rank Fusion: Combining Ranked Lists
  3. 3Weighting the Blend
  4. 4MMR: Killing Redundancy in the Top-k
  5. 5AskHelpwell v2: Hybrid + Diversity
70 min5 sections
Open module
05
Module 5

Scaling Search

AdvancedPro

Topics include Brute force cost, IVF / k-means, HNSW graph walk, and more.

View 5 sections
  1. 1Brute Force Has a Ceiling
  2. 2IVF: Searching the Right Neighborhood
  3. 3HNSW: Navigating a Graph of Vectors
  4. 4Quantization: Trading Precision for Memory
  5. 5The Recall-vs-Speed Dial
70 min5 sections
Open module
06
Module 6

Re-Ranking & Measuring Retrieval

AdvancedPro

Topics include Bi- vs cross-encoder, Two-stage retrieval, Recall@k, and more.

View 5 sections
  1. 1Bi-Encoder Recall vs Cross-Encoder Precision
  2. 2Two-Stage Retrieval: Retrieve Wide, Re-Rank Narrow
  3. 3Recall@k and MRR
  4. 4nDCG: Grading the Whole Ranking
  5. 5AskHelpwell v3: Measured End to End
70 min5 sections
Open module
07
Module 7

Query Transformation

AdvancedPro

Topics include HyDE, Multi-query, Step-back, and more.

View 5 sections
  1. 1When the Question Is the Problem
  2. 2HyDE: Retrieve With a Hypothetical Answer
  3. 3Multi-Query and Step-Back
  4. 4Decomposition: Multi-Hop Questions
  5. 5AskHelpwell v4: Rewriting the Question
65 min5 sections
Open module
08
Module 8

Grounding, Citations & Answer Evaluation

AdvancedPro

Topics include Context assembly, Grounding, Citations, and more.

View 5 sections
  1. 1Assembling the Context Window
  2. 2Grounding and Citations
  3. 3Knowing When to Say "I Don't Know"
  4. 4Did Retrieval Actually Work? Answer-Level Evaluation
  5. 5AskHelpwell Final: Grounded, Cited, Evaluated
70 min5 sections
Open module
Who this course is for

Built for people who need to use the skill.

01

AI engineers building RAG applications

02

Search and data practitioners

03

Technical teams evaluating vector databases

Start the course

Begin with The Retrieval Problem.

The first module establishes the language and example used throughout the rest of the course.

Open Module 1
Building RAG Systems & Vector Search | Let's Data Science | Let's Data Science