Microsoft — Software Engineer ❌ Failed
Level: Mid-Level
Round: Onsite · Type: Multiple Types · Difficulty: 7/10 · Duration: 240 min · Interviewer: Unfriendly
Topics: API Design, Idempotency, Data Structures, Breadth-First Search, Rate Limiter, Sliding Window, System Design, ETL, Load Balancing, Caching, Asynchronous Queue
Location: Redmond, WA
Interview date: 2026-01-10
Got offer: False
Summary
Round 1: Coding
Question: Implement an idempotent API with an idempotency key. I struggled to fully implement the API and could only use a map to track idempotency key usage.
Round 2: Coding
Question: Determine the minimum number of moves to solve a 15-puzzle using BFS.
Round 3: Coding
Question: Implement a rate limiter's allow function using a sliding window. I didn't finish writing the test cases.
Round 4: System Design
Question: Design a job scheduler's ETL pipeline system, covering topics like load balancing, caching, and asynchronous queues.
Details
Preparation Tips & Key Takeaways
What I Learned
- Implementing idempotency correctly in APIs requires careful handling of state and potential race conditions.
- BFS is a fundamental algorithm, and I need to be very comfortable with its implementation.
- Time management is crucial during coding interviews, especially when test cases are involved.
- System design interviews often cover common patterns like load balancing and caching.
Recommended Preparation
Coding Practice
- Practice implementing idempotent APIs with various approaches.
- Review BFS and other graph traversal algorithms.
- Work on time-constrained coding challenges.
System Design
- Study common ETL pipeline architectures.
- Understand the trade-offs between different load balancing strategies.
- Familiarize myself with caching techniques and asynchronous queue implementations.
Resources I Recommend
- LeetCode for coding practice.
- System Design Primer for system design concepts.
- Books on API design and distributed systems.
Common Pitfalls to Avoid
- Not fully understanding the requirements of idempotency.
- Failing to complete test cases during coding rounds.
- Lacking a structured approach to system design problems.