StubHub Senior+ Software Engineer Interview Experience — Rejected After Onsite With No Feedback

Coding round:

# StubHub Event Recommendation / Marketing Engine
#
# You are building part of a marketing engine for StubHub.
# The system runs different recommendation campaigns that find
# relevant events for a customer and generates notification text.
# ------------------------------------------------------------
# Part 1
# ------------------------------------------------------------
# Define a MarketingEngine class and implement a method like:
#
#     send_customer_notifications(customer: Customer) -> None
#
# that notifies the customer of all events happening in the same city
# as the customer.
# ------------------------------------------------------------
# Part 2
# ------------------------------------------------------------
# Extend the solution with a new campaign:
#
# notify the customer with the single event whose date is closest
# to the customer's next upcoming birthday.
# ------------------------------------------------------------
# Part 3
# ------------------------------------------------------------
# Add another campaign:
#
# notify the customer with the 5 closest events based on geographic distance
# between the customer and the event.
# ------------------------------------------------------------
# Part 4
# ------------------------------------------------------------

Open discussion about how to improve the recommendation.

System design

Design an internal chat system for StubHub that also has the ability to send notification emails to customers who haven't logged in for 10 days.

Result

Two days later I got a notification from the recruiter that I'd failed both the coding and system design rounds. No detailed feedback.

For the coding round, I finished writing the code in about 40 minutes. The interviewer said good job, then we just chatted for another thirty minutes.

For the system design round, I missed one point in the middle: how to route bi-directional websocket communication between multiple servers. After the interviewer called it out, I added Redis pub/sub. I finished the problem in about forty-five minutes, then spent ten minutes discussing what changes I'd make to improve the system if I were the PM, plus five minutes of Q&A.

I genuinely can't figure out why I failed — I emailed asking for detailed feedback and never got a reply. The first interviewer was very friendly — he happened to have come from the same company I used to work at, and we talked a lot about what it used to be like there — so I really didn't expect to get failed right after that. The second interviewer kept pushing for a high-level design, but I wanted to clarify details step by step; he didn't say much, and whenever I finished a part and asked how it looked, he'd just throw out another question. At the end he said "good job, your system would work good," then started asking what I could improve going forward. I have no idea what this company's bar is, but at the mid-senior level I don't know where the gap was.