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Interview experiences

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Interview experiences · Cisco
Cisco Software Engineer interview: a broad and difficult online assessment
The OA was difficult from the beginning and covered far more than I'd expected. It mixed multiple-choice questions, coding and several subjective scenario sections. One section used short passages followed by questions I had to answer in words. Switching from coding to those judgment-based tasks was immediately challenging. The coding was hard too, requiring both speed and correctness. My backgro…
Interview experiences · Cisco
Cisco Software Engineer interview: assessment followed by weeks of silence
My process began with a Hackerrank-style exam. It included several easy-to-medium LeetCode-style problems and a simple SQL question, so it felt manageable compared with harder online assessments I had heard about. After I finished, I heard nothing for weeks. The silence eventually ended without further progress, so the outcome felt less like the result of an interview conversation and more like a…
Interview experiences · Cisco
Cisco Software Engineer interview experience
The technical questions leaned toward systems thinking and networking fundamentals. I was asked about stack and heap basics, what causes segmentation faults, and how I would approach debugging a stack overflow. Networking came up too, including wireless concepts and the differences between OFDMA and OFDM. The conversation stayed informal. Even when the topics got detailed, I was encouraged to exp…
Interview experiences · Cisco
Cisco Software Engineer Interview Experience — HR Screen, Then a River-Crossing Brainteaser Instead of Coding
I applied for an SDE role on the Switch team. The first round was over Wedex, 30 minutes, with a female HR person. She asked things like where I live and where I'm eligible to work — that kind of question, nothing about my past experience. At the end I asked her how to prepare for the next round. She said this one would be switch-related, so I should probably brush up on some switching fundamenta…
Interview experiences · Cisco
Cisco Software Engineer Interview Experience — QA Questions from an Acquired Team
This was a team from a company Cisco acquired. The questions were mostly about my experience and open questions, and these interviews really come down to luck, so these are just the ones I remember. Everyone was pretty nice and happy to share their own experiences. If you can successfully ping a server, does that mean port 443 is accessible? How do you test a new feature? How do you drive improve…
Interview experiences · Cisco
Cisco Software Engineer Interview Experience — Rejected for Background Mismatch After a Resume-Heavy Technical Screen
My first round was a technical phone screen with a TL. They said it was technical, but since my experience and the role (low level/embedding) weren't a great match, they spent a lot of time deep-diving into my resume. On top of that, my big-tech infra project architecture was fairly simple, and I had to explain some of the tools I'd used, so before I knew it, 50 minutes were gone. The coding ques…
Interview experiences · Cisco
Cisco Software Engineer interview: fair questions and disputed cheating concern
I entered the interviews confident because the questions matched my strengths: backend concepts, Java, system design, and coding. The interaction felt positive, and I believed I answered clearly. After the rejection, I spoke with HR to understand what happened. I learned that the interviewer thought I was looking at answers during the interview. That surprised me because I was not using anything…
Interview experiences · Cisco
Cisco Software Engineer interview: networking OA cutoff
The process began with an online assessment, and the later interview path depended on that result. For me, the OA was the gate. I solved some questions, but my overall performance was not strong enough to continue. There was no detailed technical follow-up afterward, only the sense that the feedback did not support moving forward. The assessment covered networking and C fundamentals: subnetting,…
Interview experiences · Cisco
Cisco Software Engineer interview: OA programming barrier and design discussion
My process started with an online assessment and moved quickly into interview rounds, though I did not make it all the way through. The assessment combined many multiple-choice questions with programming tasks, and I could tell early that the programming section would decide things. When I was unsuccessful, the gap was clearly more about solving than simply understanding concepts. The interviews…
Interview experiences · Citadel
Citadel Data Scientist Interview Experience — A Late, Awkward Interviewer and One Linear-Fit Question
The technical interview was supposed to be 30 minutes, but the interviewer showed up 5 minutes late. Fine, whatever. Then he introduced himself, and the whole thing was really awkward — he stumbled over his words the entire time, and all he actually said was his name and his job title. Then he just froze there, like maybe he was supposed to say something about the company, but he said nothing at…
Interview experiences · Citadel
Citadel Data Scientist Interview Experience — Temperature Models, Interpolation, and Streaming Regression
First question Background You are given daily temperature data for P towns and daily temperature data for New York City over the same N days. Write functions to answer several questions. Part One — five questions Q1: Which place, either one of the towns or New York City, has the greatest temperature variation, measured by standard deviation? Q2: When Town2's temperature is between 90 and 100 degr…
Interview experiences · Citadel
Citadel Intern Software Engineer Interview Experience — A Course Schedule Variant That Didn't Quite Run
This was for a 2027 summer internship, interviewing in the summer before my junior year. The first 15 minutes were self-introduction plus resume questions. The resume question was pretty vague — the interviewer only asked one question, but it actually bundled two things together: my most technically challenging experience, and whether I had a feature that directly helped with product commercializ…
Interview experiences · Citadel
Citadel Intern Software Engineer Interview Experience — A Deep Dive on the Classic Orderbook Problem
This was my second round for the Citadel SWE intern process. The technical part was the classic orderbook problem. The question was the classic orderbook problem. Problem description: Design and implement an order book data structure that maintains order records containing the exchange name, price, quantity, and side (bid or ask). It needs to support three core APIs: add(exchange, price, quantity…
Interview experiences · Citadel
Citadel Intern Software Engineer Interview Experience — File Deduplication, Size Checks, and Reference Counts
My first Citadel SWE interview. The interviewer was on the hedge fund side. I gave a brief introduction. Before I had a chance to tell the behavioral stories I'd prepared, he went straight into technical questions. The interview was basically 100% coding and system design. Problem: Suppose a file system contains files with identical contents. For example, /a/b/c.txt and /a/b/e.txt both contain th…
Interview experiences · Citadel
Citadel Intern Software Engineer Interview Experience — Merging K Timestamped Price Feeds into a Running Price in Technical Round 3
Citadel SWE intern technical interview. The interviewer was from Citadel Securities. Problem description: You are given K data streams (feeds), and each feed is already sorted by timestamp in ascending order. Each event has two fields: a timestamp and a price delta. Requirement: merge the events from all the feeds in time order, and after processing each event, output the current cumulative absol…
Interview experiences · Citadel
Citadel Securities C++ SWE Interview Experience — Onsite Design Round Interrupted Nonstop by a Confused Interviewer
I just finished interviewing for Citadel Securities' C++ SWE position, and the whole experience was very negative, so I'm posting here to vent. The phone screen was an external merge sort with a heap. The interviewer was decent, and the overall experience was fine. After that, they quickly scheduled the onsite and told me there'd be five rounds total: design + 2h coding + 1h code review + 1h proj…
Interview experiences · Citadel Securities
Citadel Securities Research Engineer Interview Experience — I Built a Transformer When a Decision Tree Would Do, Then Got Ghosted
I work in tech. Every time I get ready to switch jobs, a pile of workload drags me back, so I just kind of go with the flow. Three months ago (I had 4.5 YOE at the time), a recruiter reached out saying some trading companies could do 3-days-a-week hybrid in Florida. Then the team they actually lined up didn't match the pitch lol, they said it was New York only. I wasn't that interested and honest…
Interview experiences · Citadel Securities
Citadel Securities Software Engineer Interview Experience — Lock-Free Producer-Consumer, Currency Arbitrage, and an Order Book
Implement a threaded producer-consumer, optimize from a mutex and then a spin lock. A list of currency conversions: determine if an arbitrage opportunity exists. Find the sequence of conversions to make money. Implement an order book data structure: maintain the order of incoming ask/bid/qty price, aggregate. Cancel an order without impacting other orders. Implement a smart queue: maintain the or…
Interview experiences · Citadel Securities
Citadel Securities Software Engineer Interview Experience — Trade Data and Timestamp Precision
The author reports a Citadel Securities process with an initial recruiter screen and two technical interviews, without an online assessment. A New York team lead conducted a one-hour session involving trade reconciliation, behavioral questions, and design follow-ups. A London lead then held a longer-than-scheduled interview combining another trade-data task with detailed resume discussion. The ac…
Interview experiences · Citadel
Citadel Software Engineer Interview Experience — 2027 OA, Two Problems in 75 Minutes
There were two problems, with 75 minutes in total. First problem: Given an initial work schedule for n days, an employee earns a fixed amount for each working day. If the previous day was also a working day, the employee earns an additional bonus. The employee may change at most k days off into working days, but may not change a working day into a day off. The goal is to choose which days off to…
Interview experiences · Citadel
Citadel Software Engineer Interview Experience — A Maddeningly Vague Data Sampling Question
Citadel is out of their minds. The first half was fine — a normal self-introduction, project walkthrough, basic behavioral questions. Then the coding part started and that's where the craziness began: The interviewer was mumbling and couldn't speak clearly, and gave me a purely verbal problem: "we have millions of data points that need to be labeled," and told me to find the useful data. I kept f…
Interview experiences · Citadel
Citadel Software Engineer Interview Experience — HackerRank OA, Two Coding Problems in 75 Minutes
I did this OA on the HackerRank platform. Two questions, 75 minutes. Q2: You're given n employees' office hours as intervals [startTime[i], endTime[i]]. You need to build a team that includes at least one "core employee" whose working hours overlap with every other member's working hours. Find the maximum number of employees the team can include. For example: Input: startTime = [2, 5, 6, 8], endT…
Interview experiences · Citadel
Citadel Software Engineer Interview Experience — OA Questions Matched a 1point3acres Compilation
I was tested on the last two of these. My solutions passed all the test cases. All of the questions below are from 1point3acres. Prefix Count of "10" Given a binary string sequence of length n, you can perform the following operation any number of times: append a '0' or '1' to the end of the sequence. After updating the sequence (i.e. appending characters to the end of the original sequence), if…
Interview experiences · Citadel
Citadel Software Engineer Interview Experience — Optimizing a Correct C++ Function to Run Under 100 Microseconds
The assessment provided C++ source code for a root_node function. Its logic was correct, but it ran extremely slowly. The task was to refactor and optimize it so that it would finish in strictly less than 100 microseconds on large inputs. The original code contained nested loops and operations such as std::find_if and std::advance, producing O(N²) complexity. I needed to reduce that to O(N). It a…