Snap Software Engineer interview questions

117 Software Engineers have shared notes from their Snap interviews, with the questions they were asked in each round. That is 54% of the 216 Snap interview notes on Screna AI.

117 Software Engineer interview notes

Snap·Software Engineer·Technical Phone Screen

Jul 2026
Snapchat software engineer interview with two fairly distinct coding problems. One was a geometry/graph problem and the other was a tree-building exercise with a follow-up on mutations. Nothing too wild but the DOM question had more depth than I expected.
  • You're given a set of 2D circles representing stones in a river. Determine whether the stones collectively block the full width of the river. You can define your own input format.
  • Given a sequence of HTML-like tokens (for example: open paragraph, raw text 'ABC', close paragraph), parse them and build a DOM tree, then print it. Follow-up: add support for inserting and deleting nodes.

“The 'define your own input format' part threw me a little, felt like a trick but it's probably just them being flexible.”

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Snap·Software Engineer·Technical Phone Screen

Jul 2026
Snapchat SWE interview with a classic dynamic programming problem. Pretty standard coding round, nothing too surprising, but the edge cases around zeros will trip you up if you're not careful.
  • Given a string of digits, count the total number of ways to decode it into letters using the mapping where '1' maps to 'A', '2' to 'B', and so on up to '26' mapping to 'Z'. Substrings like '06' or '30' are invalid.

“The base logic clicked pretty fast for me, single digit or two digit, build up a dp array.”

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Snap·Software Engineer·Technical Phone Screen

Jul 2026
Snapchat software engineer interview with a BFS/graph problem. Pretty standard algorithmic round but the deadend constraint is the part that trips people up if they're not careful.
  • You start with a lock at '0000'. Given a target combination and a list of forbidden states, each turn you can rotate any single digit up or down by one (wrapping 9 to 0 and vice versa). What's the minimum number of moves to reach the target without hitting any forbidden state?

“Classic BFS setup once you see it, but I spent an embarrassing amount of time trying to think about it as a graph problem before realizing it basically IS a graph problem and BFS just falls out naturally.”

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Snap·Software Engineer·Technical Phone Screen

Jul 2026
Snapchat software engineer interview that was pretty much all binary search variations. They pushed hard on both iterative and recursive implementations plus complexity analysis, which I wasn't fully expecting.
  • Given a sorted integer array and a target value, return the index of the first element that is greater than or equal to the target. Implement it both iteratively and recursively, handle duplicates, analyze the time and space complexity, and then explain how you'd modify the approach to find the last element less than or equal to the target.

“The iterative part was fine, lower bound binary search, nothing too bad.”

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Snap·Software Engineer·Technical Phone Screen

Jul 2026
Snapchat software engineer technical phone screen. One graph/BFS-style problem, pretty standard stuff but the exact boolean-only constraint tripped me up a little because I kept wanting to return the path length out of habit.
  • Given a start word, an end word, and a dictionary of valid words, determine whether it's possible to transform the start word into the end word by changing exactly one letter at a time, where every intermediate word must exist in the dictionary. Return true or false.

“My first instinct was BFS and that was correct, but I wasted a few minutes mentally solving for shortest path length before re-reading and realizing they just wanted a boolean.”

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Snap·Software Engineer·Technical Phone Screen

Jul 2026
Snapchat SWE interview with a data structures and algorithms question that looked deceptively simple on the surface but had a lot of layers once you got into the query optimization part.
  • Given an unsorted list of timestamp events (with possible duplicates), implement a query(start, end) function that returns the count of events falling within the inclusive time range [start, end].

“My first instinct was to just sort the list and do two binary searches, which gets you most of the way there.”

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Snap·Software Engineer·Technical Phone Screen

Jul 2026
Snapchat SWE interview with a classic graph/celebrity problem. Pretty focused session, one meaty algorithmic question with a follow-up on verification logic.
  • Given n people labeled 0 to n-1, find the 'celebrity' using an API that tells you whether person A knows person B. A celebrity is known by everyone but knows no one. Solve it in O(n) API calls, or return -1 if no celebrity exists.

“The O(n) constraint is what makes this interesting.”

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Snap·Software Engineer·Technical Phone Screen

Jul 2026
Snapchat SWE interview with a deep parallel systems follow-up that honestly caught me off guard. The core problem was already tricky but then they pushed into multi-threaded territory and I had to think on my feet about trade-offs I hadn't fully prepared for.
  • If you have multiple threads available, how would you parallelize a BFS solution for the rotating-lock problem? Walk through how you'd split work across threads, keep level ordering intact, build a thread-safe visited set and queues, avoid re-exploring the same state, and weigh the trade-offs around contention, memory, and whether the result stays deterministic.

“This one went sideways pretty fast.”

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Snap·Software Engineer·Take-home Assignment

Jul 2026
Snapchat SWE interview where they had me build a tappable color-changing grid in iOS, either SwiftUI or UIKit, right there in Xcode. Pretty hands-on, more of a practical coding exercise than a whiteboard thing.
  • Build a scrollable grid of squares with a fixed number of rows and columns. Tapping a square should toggle or change that cell's color. Use SwiftUI or UIKit and run it locally in Xcode.

“I went with SwiftUI and LazyVGrid because I knew it cold.”

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Snap·Software Engineer·Onsite - System Design / Architecture

Jul 2026
Snapchat system design round focused entirely on ad infrastructure, specifically how you'd track impressions and spend at scale and then serve that aggregated data back to the ad server fast enough to be useful. Pretty deep dive, more backend-heavy than I expected for an ads-adjacent role.
  • Design a system that tracks ad impressions and ad spend at scale, and serves aggregated data back to the ad server with low latency, given that each user request involves looking up data for roughly 10,000 candidate ads.

“The 10k candidate ads per request detail is what made this tricky.”

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