Microsoft Software Engineer Interview Experience — Four Rounds, Best Vibe I Had All Year

Four rounds, overall a really relaxed vibe.

Posting my Microsoft interview experience to give back to the forum. Bottom line up front: this was the most comfortable-feeling interview I had all year. The interviewers were pretty much all friendly, nobody tried to trip me up on purpose, and when I got stuck they'd proactively throw me a rope. The questions were medium difficulty, but they cared a lot about code quality and communication — getting it working with sloppy code didn't necessarily look good.

Round 1

The interviewer had a frontend background. He spent the first ten minutes just talking about what his team does, saying "I want you to know what you'd actually be working on before you decide how seriously to answer my question," which felt nice.

The question was Spiral Matrix — print a 2D array clockwise as a 1D array.

All the difficulty here is in boundary handling. I used four boundary variables — top, bottom, left, right — and shrank the relevant boundary after finishing each edge. Two things I was especially careful about while writing:

First, the right-to-left and bottom-to-top passes need an extra check, otherwise a single-row or single-column matrix gets double-printed. I called out this pitfall before I even started writing, and the interviewer said "good, most people only find this out by running a test case."

Second, I used top <= bottom && left <= right as the loop termination condition instead of counting output length.

After I finished he had me run three cases: a 1x5 single row, a 5x1 single column, and a 3x3. All correct.

The follow-up was how to do it counterclockwise. I said just swap the order of the four edges — the boundary-shrinking logic doesn't change at all. Then he asked, "what if it's spiral fill — given n, generate an n x n spiral matrix?" I said the framework is identical, you just change reads to writes. He seemed pretty satisfied with that answer because it pointed out that the two problems share the same skeleton.

Round 2

This round leaned more toward design and implementation.

The question was implementing an LRU cache where both get and put are O(1).

The classic hash map plus doubly linked list combo. While writing it I made a point of doing two things:

First, I defined my own Node class and wrote two private methods, removeNode and addToHead, which made the logic inside get and put very short. The interviewer explicitly said "I like that you pulled those two out." This confirmed what people on the forum say — Microsoft cares a lot about code organization, not just whether it runs.

Second, I used dummy head and tail nodes to avoid a bunch of null checks.

After I finished, the follow-ups were the main event:

What if it's accessed by multiple threads? I said the simplest approach is a single lock over the whole cache, but concurrency would be bad. The improvement is sharded locking — hash keys into several segments, each segment has its own lock and its own linked list, so operations on different segments can run in parallel. He pushed further: "is it still strict LRU after sharding?" I said no, it becomes an approximation of LRU within each shard — you're trading precision for concurrency. He said that answer was right on target.

What about supporting expiration? I said you could add an expiry timestamp on the Node, check it lazily on get, and also run a background thread for periodic cleanup.

What if the cache needs to span multiple machines? We only talked about this at a high level — consistent hashing for sharding, with each node internally still using the same structure.

This was the round I felt I got the most out of, out of all four. The follow-ups kept climbing, and each layer switched a different dimension: single machine to concurrent, stateless to expiring, single machine to distributed.

Round 3

The interviewer was the only one of the four who had me write two problems.

The first was determining whether a linked list is a palindrome, in O(1) space.

The approach was fast/slow pointers to find the midpoint, reverse the second half, then compare front and back. After I finished, she asked something I hadn't anticipated: "you broke the linked list — can you restore it?" I froze for a second, then said you could reverse the second half again after the comparison to put it back. She said this actually matters a lot in real engineering, because callers don't want their data structure mutated by a function they called. I made a note of that — genuinely an angle I'd never considered while grinding practice problems before.

The second was the zigzag level-order traversal of a binary tree.

Standard BFS plus a direction flag, even levels left to right, odd levels right to left. I used a deque and inserted from either end to avoid reversing each level afterward. She asked "can you do it with a stack?" I said yes, two stacks alternating, but the code would be longer and less intuitive than the queue approach.

We finished both problems with five minutes left and spent it talking about her team's tech stack.

Round 4 — As Appropriate

This round was with someone at a more senior level, usually called the "AA round." No coding — the conversation covered a lot of ground.

Questions asked:

• Describe the best-designed system you've worked on, and what makes it good
• Talk about something you later realized you'd designed wrong
• Have you had disagreements with a PM? How did you handle them?
• If you were dropped into a domain you know nothing about, how would you get up to speed?
• How do you decide whether a technical proposal is worth doing?

For the second question I talked about a stopgap I'd built to hit a deadline that gradually turned into long-term tech debt, walking through how it decayed step by step and how I eventually pushed to refactor it. He followed up with "how did you convince others to spend time paying down that debt?" I said I used data — I tracked how many engineer-hours per quarter that piece of code was eating.

For the fifth question I said you first look at how big the problem it solves is and how many people it affects, then look at implementation and maintenance cost, then check whether there's a simpler alternative. He came back with "what if the benefit is hard to quantify?" I said then you build a minimal validation first and let real data decide, rather than guessing.

This whole round felt conversational, not adversarial, but the questions were all substantive.

Some advice

1. Microsoft cares a lot about code quality itself. Pulling out helper methods, naming variables clearly, calling out boundary conditions before you write them — all of that scores points. I got positive feedback on code organization in two separate rounds.

2. The direction of follow-ups is "change the dimension," not "add difficulty." Single machine to concurrent, stateless to stateful, single machine to distributed — prepare those three directions and you'll cover most of what comes up.

3. Pay attention to side effects in your functions. The palindrome linked list question taught me a lesson — mutating a caller's data structure is a real sin in actual engineering, and bringing it up proactively during the interview makes you look experienced.

4. The AA round is testing judgment, not knowledge. How you decide whether something is worth doing, how you ramp up in an unfamiliar domain — you need your own framework going in for these, you can't improvise one on the spot.

5. A relaxed atmosphere doesn't mean a low bar. The less pressure an interviewer puts on you, the more you need to proactively say everything that needs saying yourself, because they won't chase you for it.

Wishing everyone good luck.