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Zipline

Mid-sized

Screna has 13 Zipline interview write-ups. The most reported round is the technical phone screen (6).

13 interview notes · updated Jul 2026

Zipline·Software Engineer·Technical Phone Screen

Jul 2026
Zipline software engineer interview, got a data structures problem that looked straightforward but had a nasty twist with the popMax operation. Pretty much a pure coding round, no behavioral fluff.
  • Design a stack data structure that supports push, pop, top, peekMax, and popMax operations, where popMax removes the maximum value closest to the top if there are duplicates. Discuss the time complexity of each operation.

“The push/pop/top part I had down immediately.”

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Zipline·Software Engineer·Technical Phone Screen

Jun 2026
Interviewed at Zipline with a focus on past work and research experience, specifically the technical details of projects tied to the role. Pretty standard deep-dive format, nothing too surprising.
  • Walk me through your past work and research experience, focusing on the technical details of projects most relevant to this role.

“This was basically the whole interview.”

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Zipline·Software Engineer·Onsite - System Design / Architecture

Jun 2026
System design round at Zipline for a software engineering role. The prompt was a railroad crossing control system, which sounds niche but actually covers a ton of ground: sensors, actuators, redundancy, failure modes. More depth required than I expected going in.
  • Design a safe and redundant control system for an at-grade railroad crossing, covering train detection, road user warnings, gate control, failure handling, and maintenance support.

“This one is deceptively wide.”

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Zipline·Software Engineer·Onsite - Coding / Algorithms

Jun 2026
Zipline robotics coding round where you build a checkers game simulation collaboratively with the interviewer in about an hour. The architecture design piece came first, then they jumped in to co-write some functions while I was expected to own the core algorithm modules. Felt less like a solo grind and more like a pair programming session, which I wasn't fully prepared for.
  • Design and implement a checkers game simulation with clean object-oriented architecture, then build out the core game logic modules collaboratively with the interviewer.

“The OOP design part was fine but I underestimated how much they'd scrutinize interface definitions before letting us move forward.”

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Zipline·Software Engineer·Technical Phone Screen

Jun 2026
45-minute session at Zipline for a software engineer role, basically a code review where they handed me a 1D filter implementation and asked me to tear it apart. Not your typical coding round.
  • Given a 1D filter implementation, identify and explain the deficiencies or bugs in the code.

“This was the whole interview.”

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Zipline·Software Engineer·Technical Phone Screen

May 2026
Interviewed for a software engineering role at Zipline and got hit with the classic largest rectangle in histogram problem. Pretty standard algorithmic screen, nothing too surprising if you've done competitive programming before.
  • Given an array of bar heights, find the maximum area rectangle that can be formed using any contiguous range of bars, where the rectangle height is bounded by the shortest bar in the chosen range.

“Classic monotonic stack problem.”

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Zipline·Software Engineer·Technical Phone Screen

May 2026
Zipline gave me a system design coding question that was basically 'build a checkers simulator OOP style' and I spent most of the time second-guessing my class hierarchy. Solid technical round, nothing behavioral, just deep in the weeds on design and implementation.
  • Design and partially implement an object-oriented simulator for a two-player checkers-like board game, covering class design, public APIs, core algorithms, and edge case handling.

“This one is bigger than it looks.”

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Zipline·Software Engineer·Take-home Assignment

May 2026
Take-home assignment for a software engineering role at Zipline. The task was to implement a Kalman filter in Rust, specifically targeting embedded systems constraints, with a heavy emphasis on code quality and data-oriented design.
  • Implement a Kalman filter in Rust optimized for embedded systems, with a focus on code quality, engineering rigor, and a data-oriented design approach.

“This one took a while to scope properly.”

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Zipline·Software Engineer·Onsite - System Design / Architecture

May 2026
Technical review round at Zipline for a software engineering role, focused entirely on embedded systems and signal processing. Two meaty problems back to back, both requiring you to think about real constraints rather than just algorithmic correctness. Left feeling like I probably undersold some of my embedded experience.
  • You're building a real-time 2.5D elevation mapping system on an embedded computer. Given timestamped 3D sensor points and vehicle poses, how would you design the data structures, update logic, and optimizations to meet CPU, memory, and latency constraints?
  • There's a causal 1D filter in the codebase used to smooth a noisy sensor signal. Without seeing the code, what correctness, robustness, and testing issues would you look for, and how would you address them?

“This is where I spent most of my mental energy.”

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Zipline·Software Engineer·Technical Phone Screen

May 2026
Zipline gave me a 45-minute technical screen with a single hard algorithm problem. No warmup, no small talk, just straight into it.
  • Given an array of bar heights representing a histogram, find the area of the largest rectangle that can be formed.

“This is the classic monotonic stack problem and I knew I'd seen it before, which somehow made it worse because I second-guessed myself the whole time.”

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