Capital One Software Engineer interview questions

93 Software Engineers have shared notes from their Capital One interviews, with the questions they were asked in each round. That is 24% of the 382 Capital One interview notes on Screna AI.

93 Software Engineer interview notes

Capital One·Software Engineer·Onsite - Multi Round

Oct 2026
Did the Capital One TIP Power Day last Friday, three back-to-back rounds: behavioral, a case/coding section, and an agentic coding round. The coding case tripped me up a bit but everything else felt solid. Waiting to hear back and kind of spiraling about whether the unfinished implementation tanks the whole thing.
  • Behavioral interview questions covering your background and experience.
  • True/false concept questions as part of a technical case round.
  • Debugging exercise: identify and fix bugs in existing code.
  • Implement a function from scratch as the final part of the case round.
  • Agentic coding round: fix a bug, implement a new feature, and suggest improvements to the codebase.

“This part went fine.”

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Capital One·Software Engineer·Online Assessment (OA)

Oct 2026
Took the Capital One Senior Full Stack Engineer OA in early October, four questions in 70 minutes. Flew through the first three but got burned by hidden test cases on the last one due to timeouts. Rejection came four days later.
  • An easy warm-up question (specific details not recalled).
  • Given a lowercase sentence, sort the words by the absolute difference between the number of consonants and vowels in each word. Break ties alphabetically and return the sorted list.
  • Given a grid with healthy plants, infected plants, and empty cells, return the state of the grid after exactly X days of infection spreading (similar to the Rotting Oranges problem, but with different thematic labels).
  • Design a system supporting two operations on a number line: (1) place an obstacle at position X, and (2) given a coordinate L and a range size N, check whether any obstacles exist in the window from L minus (N-1) to L plus (N-1). Return a string of 0s and 1s for all type-2 queries.

“Can't even remember what it was, which probably tells you how trivial it felt.”

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Capital One·Software Engineer·Onsite - Multi Round

Sep 2026
This is a compiled breakdown of Capital One's TDP Associate 'power day,' covering three main segments: an agentic coding portion, a case study, and behavioral questions. The agentic section uses a full stack codebase with Claude as an AI assistant, which threw me off since most prep material out there is built around a totally different company's setup. The case study is manageable if you can communicate clearly, but you can't run any code, which makes it stressful.
  • You're given a large, unfamiliar codebase. Find and fix a bug within 20 minutes, then discuss your approach.
  • Implement a new feature in the same unfamiliar codebase within 20 minutes, then walk through your decisions.
  • Walk through this business scenario, manually trace the rules described, debug the code implementing those rules, and then add a new method with similar logic.
  • Tell me about a time you challenged the status quo.
  • How do you use AI tools in your day-to-day work?

“The catch nobody warns you about: most prep resources describe a much smaller codebase with simpler logic.”

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Capital One·Software Engineer·Online Assessment (OA)

Aug 2026
Took the CodeSignal OA for a staff engineer role at Capital One, four problems, and it did not go great. Finished one cleanly, hit TLE on another, had a bug I couldn't track down on the third, and barely touched the fourth. Ended up with 347/600 and now I'm just waiting to see if one of my two applications survives.
  • CodeSignal OA Problem 1: A straightforward coding problem (exact problem not specified).
  • CodeSignal OA Problem 2: A coding problem requiring an optimized solution beyond a brute-force approach.
  • CodeSignal OA Problem 3: A coding problem where the solution logic was known but implementation had a bug.
  • CodeSignal OA Problem 4: A coding problem attempted under severe time pressure.

“This one went fine.”

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Capital One·Software Engineer·Online Assessment (OA)

Aug 2026
Took the General Assessment for a Front End Engineer role at Capital One through CodeSignal and didn't pass. Sharing the questions anyway because memorizing them felt like the least I could do after the rejection.
  • Write a function that takes an array of integers and returns a count of how many values are divisible by 3 and contain the digit 7 at least twice.
  • Simulate a two-player card game where each round the top card from each player's deck determines the winner. Return the total number of rounds played when one deck runs out.
  • Given a matrix, partition it into four submatrices by choosing one row index and one column index as the split points. Each partition must contain at least one non-negative cell. The average of a partition is the sum of its non-negative values divided by the count of non-negative values, floored. Return the row and column indices that minimize the difference between the highest and lowest partition average.
  • You are given a 2D array of lamps, where each lamp covers a segment on a number line defined by a start and end point. Given an array of control points, return an array where each element is the count of lamps whose segment includes that control point.

“Pretty approachable.”

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Capital One·Software Engineer·Technical Phone Screen

Jul 2026
Capital One data engineer technical screen focused almost entirely on gradient boosted trees applied to credit risk. Three meaty sub-questions back to back, no warmup, no small talk. Felt more like an ML engineer interview than a data engineering one, which threw me a bit.
  • How do boosted tree models handle missing values during training and inference, and when would you choose native handling over imputation?
  • What causes overfitting in boosted tree models and which hyperparameters or techniques would you use to control it?
  • For an imbalanced credit default prediction problem, which evaluation metrics would you use and how would you validate that the model generalizes well?

“I knew XGBoost learns a default direction for missing values at each split, so I led with that.”

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Capital One·Software Engineer·Online Assessment (OA)

Jul 2026
Capital One SWE interview with a grid simulation problem. Not the hardest thing I've ever seen but there are enough edge cases to trip you up if you're not careful about placement order and overlap logic.
  • Given integers n and m and an ordered list of figures (each being one of five predefined shapes), construct an n x m grid initialized to zero. For each figure in order, find the first valid top-left placement position in row-major order where the shape fits within bounds and doesn't overlap any already-placed cells. Fill those cells with the figure's 1-based index. If no valid placement exists, skip it. Return the final grid.

“The shape definitions are handed to you so that part isn't the puzzle.”

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Capital One·Software Engineer·Technical Phone Screen

Jul 2026
Capital One software engineer interview that was basically one meaty class design question about a banking account service. Not a lot of fluff, they just dropped the problem and let you run with it.
  • Design and implement an AccountService class that supports deposit, withdraw, transfer, and getBalance operations, with proper handling for insufficient funds, atomicity on transfers, and thread safety.

“The basic CRUD part was fine, I had that sketched out in a few minutes.”

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Capital One·Software Engineer·Online Assessment (OA)

Jul 2026
Capital One OA for a software engineering role. Four problems, ranging from pretty straightforward to genuinely tricky. The bubble explosion one ate up most of my time and I'm still not sure I got the gravity part right.
  • Given an array of positive integers and an integer k >= 1, count how many elements in the array are exact powers of k. Handle the edge case where k equals 1 separately.
  • On a planet where moon phases cycle every 8 days (indices 0 through 7), you're given the starting phase on day 1 and a list of month lengths for that year. For a given target date (month, day), compute the moon phase index on that date.
  • Simulate a bubble-explosion mechanic on an R x C grid: repeatedly find any 4-directionally connected group of the same color with size >= T, remove it (set to 0), then apply gravity so remaining cells fall to the bottom of their columns. Repeat until no more groups can be removed, then return the final grid.
  • Given an array of N numeric strings of equal length L (leading zeros allowed), count unordered pairs where one string can be transformed into the other using at most two character swaps within a single string. Analyze time and space complexity.

“This was the warmup and I almost tripped on the k=1 case.”

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Capital One·Software Engineer·Technical Phone Screen

Jul 2026
Capital One software engineer interview with two meaty coding problems back to back. The matrix manipulation part was fine but the street lights problem took a while to click and I'm not sure I nailed the complexity analysis on the spot.
  • Given an m×n integer matrix, implement several in-place operations: swapping two rows, swapping two columns, reversing row order, reversing column order, and rotating the matrix 90 degrees in either direction. For the rotation, handle both square and rectangular matrices and explain your time and space complexity for each operation.
  • You have a list of street lights, each defined by a position and a radius, illuminating a segment on a 1D line. Find the point covered by the most lights. If there's a tie, return the smallest such coordinate. Implement an optimal solution and analyze time and space complexity.

“The swap and reverse stuff was pretty mechanical.”

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