I have worked in the data industry for over seven years and had the privilege of designing, building, and deploying two recommender systems (RecSys) that went on to serve millions of customers. For each chapter, I will walk through case studies and share my experience designing RecSys. This is part of my Modern Visual RecSys series; feel free to check out the rest of the series at the end of the article. We begin with a case study of Spotify to understand how RecSys works and introduce several key concepts, including a modern approach called convolutional neural networks (CNN), applied to music. Let us take a look at my personalized music recommendations from Spotify. It contains a mix of Chinese/Japanese/ English pop music with new music and old tunes going back some 20 years.