🚀 Uber L4 (SDE-2 - Backend) Interview Experience (OFFER Received)
Summary
I completed Uber's L4 Backend interview process, solved all coding rounds, designed a circuit breaker and a stock price tracking system, and received an offer.
Full Experience
Hey, hope everyone is doing good. Recently finished my loop with Uber L4 and got an offer. Here are the rounds and what I got asked.
- Coding test - Hackerrank. 2 Medium-Hard questions. Was able to solve both. [PASS]
- BPS (Screening Round) - 2 DSA questions, a basic DFS evolving to Dijakstra and DFS+Binary Search. Was able to solve both in under 30 mins. Discussed some projects. [Strong Hire]
- Coding Round 1 (DSA) - 3 DSA questions. Starts from a 2D count number of islands, moved to 3D version of the same, finally moves to implementation of a 2D DSU. Was able to solve all questions, talk about Ackerman function.[Strong Hire ++]
- Coding Round 2 (LLD/Machine Coding) - Design a Circuit Breaker. The question slighly threw me off because the requirements looked like a rate limiter combined with a circuit breaker. The breaker opened when the number of requests (NOT number of errors) exceeded a threshold. Was able to solve it, come up with test cases, show OPEN, CLOSED, HALF_OPEN states and answer concurrency questions properly. [Strong Hire/Hire]
- Hiring Manager Round - Nothing unusual here. Regular "tell me about a time questions". I usually go deep into explaining the scenario and I was surprised the manager wanted me to go even into more details in some cases. Probably tired of hearing made-up stories from candidates. [PASS]
- System Design (HLD/Bar Raiser) - Design a price tracking systems for stock tickers. The requirement was to allow users to subscribe to stocks and notify them when stock price movement exceeded a DELTA value. This was a completely new problem for me and it was kinda a combination of Top-K (with sliding windows) and CamelCamelCamel. [MEETS BAR]
Key takeaways
- For HLD problems, interviewers won't necessarily let you build the basic system first before asking you to do deep dives. In essence, the Hello Interview pattern could backfire and you need to be ready in that case. I wasn't completely comfortable.
- Have some stories prepared for HM round. And real ones are better. For me the Amazon LPs prep worked good. Make sure to add anecdotes here and there to reinforce your story once in a while.
Happy to answer in any questions in the comments. Best of luck to everyone preparing for their interviews.
Interview Questions (5)
Count Number of Islands (2D)
Given a 2D grid of '0' (water) and '1' (land), count the number of distinct islands. An island is a group of horizontally or vertically adjacent '1' cells.
Count Number of Islands (3D)
Extend the classic island‑counting problem to a 3‑dimensional grid. Each cell can be '0' or '1'. An island consists of '1' cells that are adjacent along any of the three axes.
2D Disjoint Set Union (DSU) Implementation
Implement a Disjoint Set Union (Union‑Find) data structure that works on a 2‑dimensional grid, supporting union(x1, y1, x2, y2) and find(x, y) operations efficiently.
Design a Circuit Breaker
Design a circuit‑breaker component. The breaker opens when the number of requests (not errors) exceeds a configurable threshold. It must expose three states (OPEN, CLOSED, HALF‑OPEN), allow defining test cases, and handle concurrency correctly.
Design a Price‑Tracking System for Stock Tickers
Build a high‑level design for a service where users can subscribe to stock tickers and receive notifications when the price movement exceeds a user‑defined delta. The solution should handle real‑time price streams, support top‑K queries over sliding windows, and be similar in spirit to the CamelCamelCamel price‑tracking approach.