PayPal interview notes, page 1 of 10

“Took me longer than I'd like to admit to land on the self-join approach.” The rest of the author's notes on Data Scientist interview at PayPal, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.

“I went straight to groupby and size() which was the right instinct, but I initially forgot to group by both user and month together.” The rest of the author's notes on Data Scientist interview at PayPal, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.

“I went for LEAD() pretty quickly, which was the right instinct, but I initially forgot to partition by both user_id and date together.” The rest of the author's notes on Data Scientist interview at PayPal, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.

“I jumped straight into collaborative filtering and probably spent too long there before they nudged me toward cold start.” The rest of the author's notes on Machine Learning Engineer interview at PayPal, Onsite - System Design / Architecture round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.

“I went straight to the visual layer and started sketching out components before really thinking about the data flow underneath.” The rest of the author's notes on Software Engineer interview at PayPal, Onsite - System Design / Architecture round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.

“This is basically a full DS case study crammed into one question.” The rest of the author's notes on Data Scientist interview at PayPal, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.

“My first instinct was to jump straight into features, which was probably the wrong move.” The rest of the author's notes on Product Manager interview at PayPal, Onsite - Product Sense / Strategy round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.

“This felt like a trap but wasn't.” The rest of the author's notes on Data Scientist interview at PayPal, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.

“This is a big question and I think I underestimated how much they wanted me to slow down on the hypothesis piece.” The rest of the author's notes on Data Scientist interview at PayPal, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.

“The probability of winning is 15/36 since there are 36 equally likely outcomes and 15 where your roll strictly beats theirs.” The rest of the author's notes on Data Scientist interview at PayPal, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.