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Large Enterprises

Most of these Reddit write-ups come from Machine Learning Engineers (23), then Software Engineers (21) and Data Scientists (5). The most reported rounds are the technical phone screen (29), the system design round (14), the product sense round (5) and the behavioral / leadership round (3).

52 interview notes · updated Jul 2026

Reddit·Software Engineer·Technical Phone Screen

Jul 2026
Reddit coding interview that was basically a word ladder variant with a twist. The problem itself wasn't too bad once I recognized the BFS angle, but the follow-up questions on complexity and large-dictionary optimizations pushed me more than I expected.
  • Given a start word, an end word, and a dictionary of same-length words, find the shortest transformation sequence where each step changes exactly 1 or 2 characters (substitutions only) and every intermediate word must be in the dictionary. Return the path or an empty list if none exists.
  • Why would you choose BFS over DFS for finding the shortest path in this word transformation problem?
  • What is the time and space complexity of your solution?
  • How would you optimize this solution for very large dictionaries?
  • How does your solution behave when the start word is not present in the dictionary?

“I recognized the word ladder pattern pretty fast but the '1 or 2 characters' twist tripped me up for a minute.”

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Reddit·Software Engineer·Technical Phone Screen

Jul 2026
Reddit coding interview focused entirely on a reporting chain problem, basically a tree traversal setup with multiple sub-problems. The tricky part was that each sub-question had a different expected output format, which I didn't fully register until I was already mid-answer.
  • Given an employee/manager hierarchy, write a query to find who a given employee's manager is.
  • Write a query to list all direct and indirect reports under a given manager.
  • Find the lowest common manager of two given employees in the hierarchy.

“Pretty straightforward self-join on the same table.”

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Reddit·Machine Learning Engineer·Onsite - Behavioral / Leadership

Jul 2026
Prepping for a Reddit ML Engineer interview and trying to figure out how to answer the AI-in-daily-work behavioral question without sounding like a press release.
  • How do you incorporate AI tools into your day-to-day work?

“Every time I try to answer this I end up listing tools like I'm reading off a spec sheet.”

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Reddit·Machine Learning Engineer·Onsite - Behavioral / Leadership

Jul 2026
Behavioral round for an ML Engineer role at Reddit. Two questions, both the classic failure/success combo. Nothing surprising about the format but the bar for specificity felt higher than I expected.
  • Describe a time something didn't go as planned in your work. What happened, what did you take away from it, and what would you change if you could do it over?
  • Walk me through a time you succeeded at something. What specifically did you contribute and what was the measurable impact?

“I went with an incident from a model rollout that caused some downstream noise in a recommendation pipeline.”

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Reddit·Software Engineer·Technical Phone Screen

Jun 2026
Reddit system design phone screen for a software engineer role. The problem was a rate limiter with a sliding window, which sounds straightforward until you're actually in it and someone's watching you think out loud.
  • Design and implement an in-memory rate limiter using a sliding time window. The API should expose an allow(key, timestamp) method that returns whether a given request is permitted, enforcing at most N requests per W seconds per key.

“I went straight to a queue-per-key approach, storing timestamps and evicting anything outside the window on each call.”

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Reddit·Software Engineer·Technical Phone Screen

Jun 2026
Reddit SWE interview with a logic-based admin permissions question. Pretty focused, just the one problem from what I can tell.
  • Given two admin usernames, write a function that determines whether the first admin can delete the second. The rule is based on which admin was added to the system first. Return a boolean.

“Seems straightforward but the interesting part is figuring out how you're supposed to know who was added first.”

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Reddit·Software Engineer·Technical Phone Screen

Jun 2026
Reddit coding round, one big open-ended problem on rate limiting. The prompt gave you almost nothing and expected you to drive the whole design conversation yourself, which I was not fully prepared for.
  • Design and implement a RateLimiter class with an allow(key) method that returns whether a request should be permitted under a configured policy. You're expected to drive all major design decisions yourself.

“The open-endedness was the hard part.”

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Reddit·Machine Learning Engineer·Onsite - Product Sense / Strategy

Jun 2026
Reddit ML Engineer interview with a product-sense style question that felt a bit out of left field for the role. One question, pretty open-ended, and I left unsure whether I'd framed it the right way for an MLE position versus a PM one.
  • How would you redesign the onboarding experience for new users on a community platform like Reddit, covering friction identification, success metrics, prioritization, and experiment design?

“Spent the first few minutes trying to figure out whether they wanted an MLE answer or a PM answer.”

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Reddit·Machine Learning Engineer·Technical Phone Screen

Jun 2026
Reddit ML Engineer interview with a linked list problem that looks straightforward but has a few gotchas if you're not careful about pointer manipulation.
  • Given the head of a singly linked list, reorder it so all odd-indexed nodes come first followed by all even-indexed nodes, preserving relative order within each group. Must run in O(n) time and O(1) space.

“I knew the general idea pretty fast: keep two pointers, one crawling odd nodes and one crawling even, then stitch the even chain onto the end of the odd chain.”

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Reddit·Machine Learning Engineer·Technical Phone Screen

Jun 2026
Reddit ML Engineer interview, at least one round involved a coding problem around designing a tennis scoring system from scratch. More OOP-heavy than I expected for an ML role, felt like a general SWE screen dressed up as something else.
  • Design and implement a tennis scoring system as a class. It should track points for two players, return scores in both raw and human-readable formats (Love, 15, 30, 40, Deuce, Advantage, Game), handle the win condition (4+ points with a 2-point lead), prevent scoring after the game ends, and reset internal state during deuce cycles to keep things bounded.

“This took longer than I thought it would.”

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Reddit interview FAQ

What rounds are in the Reddit interview?

Candidates most often report a technical phone screen (29 write-ups), a system design round (14), a product sense round (5) and a behavioral / leadership round (3).

What does the Reddit technical phone screen cover?

Across 29 technical phone screen write-ups, the most tagged question topics are Technical Trade-offs (34 questions), Algorithms & Data Structures (28) and System Design (15).

What is asked in the Reddit system design round?

Across 14 system design write-ups, the most tagged question topics are System Design (42 questions), Technical Trade-offs (34) and Data Modeling (10).