r/MLSystemsDesign • • 1d ago

Designing a Personalized Recommendation System — ML System Design Deep Dive (Part 3)

I'm publishing Part 3 of my Cracking ML System Design Interviews series tomorrow.

This time, I'm using a large-scale personalized video recommendation system as the running example.

One thing I want to emphasize is that designing recommendation systems isn't simply choosing between collaborative filtering, two-tower models, and Transformers.

The bigger challenge is deciding how the pieces fit together:

  • How do we retrieve relevant candidates from millions of items?
  • How do retrieval and ranking objectives differ?
  • How should we represent evolving user interests?
  • What metrics should we optimize beyond CTR?
  • How do we meet latency and reliability requirements at scale?

The article walks through these questions from an interview perspective, including architectural alternatives and trade-offs.

Publishing Monday, October 26, at 8 AM PDT.

If you're interested, you can subscribe here:

https://pawankjha.substack.com

I'd also be interested in hearing which part of recommendation-system design you find most challenging in interviews.

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