Microsoft SWE Interview: Coding Interview Guide

Estimated read time: 8-10 minutes

Summary: Microsoft SWE coding interviews are a core part of the technical loop. Official guidance says technical interviews are virtual, problem-solving based, and use a third-party coding tool where code can run and compile. The source also says Microsoft evaluates coding, testing, design, engineering lifecycle, and technical excellence, so a strong coding round is more than getting a function to pass one example.

TL;DR + FAQ (read this first)

At-a-glance takeaways

• Coding interviews are expected across most Microsoft SWE levels.
• Official guidance supports runnable code in a third-party coding tool.
• Secondary sources report 4-5 virtual onsite interviews, often 45-60 minutes each.
• Expect coding plus testing, complexity, communication, and sometimes design-adjacent follow-ups.
• System design and seniority expectations vary by level and org.

Quick FAQ

Can I run code?
Official guidance says the coding tool supports running and compiling code.

Is coding expected for senior candidates?
Yes, coding remains likely, though design and leadership signals become more important.

How many coding interviews are there?
Secondary sources report 4-5 onsite interviews total, with several coding-heavy rounds, but org variance is real.

What makes Microsoft different?
Testing and engineering lifecycle are official evaluation areas, so correctness should be shown, not assumed.

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1) How coding interviews work

Microsoft technical interviews are described as problem-solving based and virtual, using Microsoft Teams plus a third-party coding tool. You may be able to run and compile code, which means the interviewer can see how you test, debug, and improve your implementation.

Rounds can mix coding with design, competency, and engineering-lifecycle discussion. Treat every coding answer as a small engineering artifact: clarify requirements, write clean code, run or walk through tests, fix issues, and explain complexity.

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2) Coding questions you may face

These examples are grounded in the source-supported Microsoft question themes and official technical signals.

• Reverse the words in a string. Then handle multiple spaces, leading spaces, and an empty input string.
• Merge intervals. Now insert a new interval and return the merged result without sorting the whole list again if it is already ordered.
• Validate a binary search tree. Then explain how duplicate values should be handled based on the requirement.
• Clone a graph. Walk through how your visited map prevents infinite recursion.
• Implement an LRU cache. Then run through get, update, eviction, and capacity-one cases.
• Find the shortest path in a graph. Then explain what changes if edges have weights.
• Design low-level classes for a parking lot or elevator system, then implement one method and test it.
• Given a failing unit test, find the bug, explain the broken assumption, and update the code.

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3) What strong coding signal looks like

Strong candidates show problem solving, coding, testing, and communication. They use the runnable environment to validate their work, then explain the complexity and edge cases.

For mid-level and senior candidates, coding may include more design pressure: class boundaries, API shape, testability, maintainability, and how the solution would fit into a larger engineering lifecycle.

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4) Common failure modes

Not running or validating code. If the tool supports execution, use that signal well.

Treating tests as optional. Testing is named in official evaluation areas.

Overlooking engineering lifecycle. Maintainability and debugging can matter even in coding rounds.

Assuming one loop shape. Round count and depth vary by org, team, and level.

Skipping follow-up reasoning. Microsoft rounds can move from code to design or competency discussion quickly.

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5) How to prepare

• Practice coding with a tool where you can run and fix tests.
• Drill strings, intervals, trees, graphs, caches, shortest paths, and low-level class design.
• After every solution, add at least three tests.
• Explain complexity and maintainability before moving on.
• For L61+ and senior candidates, practice design-adjacent follow-ups after coding.

The best coding preparation looks like real engineering: implement, test, debug, explain, and improve.

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