Amazon Interview Questions — Page 134

Amazon·Software Engineer·Onsite - Coding / Algorithms

Jun 2026

Amazon SWE coding round, one question the whole time: graph cycle detection plus topological sort. Pretty standard stuff but the implementation details can trip you up if you're not careful.

Given n courses and m prerequisite pairs, detect whether a valid course ordering exists (no cycles), and if so output one valid topological ordering of all courses.

“Kahn's algorithm with in-degree tracking is probably the cleaner approach here since you get cycle detection for free when the queue empties before processing all nodes.”

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Amazon·Software Engineer·Onsite - System Design / Architecture

Jun 2026

Amazon system design round, low-level design focus. The whole session was basically one big question about building a job scheduler from scratch, and they wanted a lot of detail across a lot of dimensions.

Design a job scheduling system that can execute a job X seconds in the future. Cover the API design, internal data structures, persistence, worker model, restart/clock drift handling, delivery semantics, concurrency, time complexity, and how you'd test it.

“This one sprawled in every direction.”

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Amazon·Software Engineer·Technical Phone Screen

Jun 2026

Amazon coding interview with two DSA questions, no behavioral stuff at all. Solved one fully and got about 90% through the second, but fumbled the space complexity on that one by forgetting to account for the input vector. Now just waiting and hoping.

First DSA problem (fully solved during the interview)
Second DSA problem (partially solved during the interview)

“Got through this one clean.”

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Amazon·Software Engineer·Onsite - System Design / Architecture

Jun 2026

Amazon system design round, one big question about building a log-processing service from scratch. The scope was genuinely wide and I'm not sure I covered everything they wanted, but it felt like a real engineering conversation rather than a trivia quiz.

Design a log-processing service that ingests application logs at scale and supports filtering by attributes, counting error-level logs over a time window, and building hourly histograms for log patterns. Cover ingestion, storage, querying, schema, deduplication, aggregation strategies, scalability, and complexity estimates.

“This thing had so many layers I didn't know where to start.”

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Amazon·Software Engineer·Technical Phone Screen

Jun 2026

Amazon SWE interview with a grid-based BFS problem that looks deceptively simple until you actually have to explain correctness and complexity out loud. One round, pretty focused.

You're given an m×n grid where cells are either empty (0), fresh fruit (1), or spoiled fruit (2). Every minute, fresh fruit adjacent to spoiled fruit becomes spoiled. Return the minimum number of minutes to spoil all fresh fruit, or -1 if it's impossible. Describe your algorithm, argue why it's correct, analyze time and space complexity, then implement it.

“Multi-source BFS from all initially spoiled cells simultaneously, that part came to me pretty fast.”

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Amazon·Software Engineer·Technical Phone Screen

Jun 2026

Amazon SWE coding round focused entirely on in-place array merging. The problem itself is LC 88 territory but the follow-ups kept stacking and I felt underprepared for the unsorted variant discussion.

Merge two sorted ascending arrays in-place, where the first array has enough trailing capacity to hold all elements from the second. No auxiliary array allowed.
Same merge problem but both input arrays are in descending order instead of ascending. How does your solution change?
What if the two input arrays are not sorted at all? Walk through your approach and the complexity tradeoffs.

“I knew this one but still fumbled the justification for going back-to-front.”

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Amazon·Software Engineer·Technical Phone Screen

Jun 2026

Applied for an SDE 2 role at Amazon, made it through the OA and into a phone screen, then got rejected. The behavioral side went fine but the coding round turned into a mess when the problem format was nothing like what I'd practiced.

Given a stream of input, process the data and write results to an output stream. The underlying problem involved string matching.
Walk me through a situation from your work experience that demonstrates how you handle a specific challenge. (Leadership principle behavioral questions with follow-ups.)
Online assessment: prefix sum style algorithmic problem (medium difficulty).
Online assessment: debug and fix a broken web project.
Online assessment: work simulation covering system design and leadership principle knowledge.

“This wrecked me.”

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Amazon·Software Engineer·Technical Phone Screen

Jun 2026

Amazon SWE coding round with three problems, two of them linked list questions and one heap/greedy problem. Nothing too wild but the mix felt a bit scattered.

Given a string, rearrange its characters so that no two adjacent characters are the same. Return an empty string if it's not possible.
Merge k sorted linked lists into one sorted linked list.
Deep copy a linked list where each node has a next pointer and a random pointer that can point to any node in the list or null.

“This one tripped me up more than it should have.”

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Amazon·Data Scientist·Technical Phone Screen

Jun 2026

Amazon Data Scientist technical screen, heavy pandas focus with four interconnected sub-problems on the same small dataset. No behavioral stuff at all, just code and complexity analysis the whole time.

Using only pandas (groupby, agg, merge, concat, no for-loops), compute Daily Active Users per device from an events table, then calculate a 2-day rolling unique user count per device aligned to day end. How do you guarantee uniqueness across days in the rolling window?
Left-join the users table to each user's first order, producing a first_order_ts column and a days_to_first_order column as a float. Users with no orders should show NaN. How do you handle users who signed up and placed their first order on the same day?
For each user, find their top 2 spending categories by total amount. Ties should be broken alphabetically. Return columns top_cat_1 and top_cat_2, with NaN for users who have fewer than 2 distinct categories.
You have a per-device daily revenue table with columns day, device, and revenue. Add a summary row labeled 'ALL' that shows total revenue across all devices for each day, then concat it back to the original table. How do you make sure column types stay consistent after the concat?

“The rolling uniqueness part tripped me up.”

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Amazon·Software Engineer·Online Assessment (OA)

Jun 2026

Amazon OA for an SWE role, one algorithmic problem on subsequence optimization. Pretty standard competitive programming flavor but the constraint size means you can't brute force it.

Given an integer array, find the maximum alternating subsequence sum, where the sum alternates between adding and subtracting elements based on their position in the chosen subsequence.

“My first instinct was greedy and I spent a while convincing myself it was correct.”

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