Recommender Systems

Collaborative filtering, matrix factorization, two-tower retrieval and the cold start problem.

Module 03.6 · Intermediate
Free

8h · 7 lessons · 0 challenges

Before this: Unsupervised Learning

About this module

Recommendation is the highest-revenue application of ML and a standing favorite in system design interviews. This module covers the classical stack — collaborative filtering and matrix factorization — then the modern two-tower retrieval and ranking split that industrial systems use.

Cold start, feedback loops and popularity bias get real treatment, since those are the follow-up questions.

After this module you can

7 lessons

Lesson 1
User-based and item-based collaborative filtering
Kind
Concept
Length
50 min
Lesson 2
Matrix factorization and implicit feedback
Kind
Concept
Length
55 min
Lesson 3
Two-tower retrieval and approximate nearest neighbours
Kind
Concept
Length
55 min
Lesson 4
Ranking, re-ranking and business constraints
Kind
Concept
Length
45 min
Lesson 5
Cold start and the exploration problem
Kind
Concept
Length
40 min
Lesson 6
Build a two-stage recommender end to end
Kind
Lab
Length
100 min
Lesson 7
Checkpoint: design the recommender
Kind
Checkpoint
Length
25 min

The challenge: Cold Start

A new user arrives with no history and you have six interactions to get them to stay. Strategy against a simulated audience.

Worth 450 XP.

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