• Status: SDE2 at Mid-sized Product Co.
• Experience: 3.5 Years
• Position: SDE2 (L61/L62)
• Location: India (Remote/Hybrid)
• Date: March 2026

Round 1: DSA & Problem Solving

• Question 1: LeetCode 124 (Binary Tree Maximum Path Sum).
• Question 2: (Similar to Trapping Rain Water 3d).
• Details: The interviewer was very focused on Edge Cases (e.g., all negative nodes in the tree). We spent the last 10 minutes discussing how to unit test these scenarios.

Round 2: Low-Level Design (LLD) / Machine Coding

• Task: Design a Task Scheduling System (like Cron/Airflow).
• Requirements:
  • Support one-time and recurring tasks.
  • Handle task dependencies (Task B starts after Task A).
  • Thread-safety for concurrent execution.
• Focus: Used the Observer Pattern for status updates and a Directed Acyclic Graph (DAG) to model dependencies. Clean code and SOLID principles were a must.

Round 3: High-Level Design (HLD)

• Task: Design Microsoft Teams Messaging Infrastructure.
• Key Areas:
  • Real-time delivery: WebSockets vs. Long Polling.
  • Scalability: How to handle a group chat with 10k+ users?
  • Storage: Partitioning strategy for chat history (NoSQL/Cassandra).
• Deep Dive: Discussed Sequence Numbers vs. Timestamps for message ordering in a distributed environment.

Round 4: AA (As Appropriate) / Hiring Manager

• Focus: Cultural fit and "Growth Mindset."
• Discussion:
  • "Tell me about a time you mentored a junior and it didn't go well."
  • "How do you handle technical debt when there is a deadline?"
• Technical: We had a brief discussion on microservices observability (tracing and metrics) to gauge my interest in the operational (“Ops”) aspects.

Final Verdict: Selected.