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Microsoft·Software Engineer·Onsite - Product Sense / Strategy·Senior

Senior
May 2026

Summary

Product design interview at Microsoft with one meaty scenario question about legacy product consolidation. Not a lot of context given upfront, which made it tricky to know how deep to go.

Questions Asked (1)

Q1

You have two similar applications, one that's been around for 10 years and one that's 3 years old. How would you approach merging them? Would you build something new or evolve one of the existing products?

Product StrategyTechnical Trade-offsAdaptability & Ambiguity
Author's notes

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AI HintsAI Generated

Suggested Approach

Start by clarifying the business goals and technical constraints, then systematically compare the two applications across dimensions like architecture, user base, and feature set. Recommend a path based on evidence, favoring evolution over a full rebuild unless the older system is fundamentally unsustainable. Emphasize incremental migration to minimize risk and deliver value early.

Pro tip: Frame your answer around reducing risk and total cost of ownership, not just technical elegance. Mention that Microsoft values data-driven decisions and customer impact, so tie your recommendation to metrics like user adoption and maintenance costs.

1. Clarify Goals and Constraints

Ask about the business objectives, timeline, budget, and non-negotiables (e.g., compliance, uptime). This ensures your approach aligns with stakeholder priorities.

2. Assess Both Applications

Compare architecture, code quality, dependencies, feature sets, user bases, and operational costs. Identify strengths, weaknesses, and overlapping functionality.

3. Evaluate Options

Consider three paths: evolve the older app, evolve the newer app, or build new. Weigh each against criteria like risk, cost, time-to-market, and long-term maintainability.

4. Recommend and Justify

Choose the best option based on your analysis, typically evolving the more modern codebase unless the older one has irreplaceable value. Explain trade-offs and mitigation strategies.

5. Plan Incremental Migration

Outline a phased approach: start with shared services or low-risk components, use feature flags and A/B testing, and gradually decommission the legacy system.

Key Points to Mention

  • Total cost of ownership: maintenance, infrastructure, and developer productivity
  • User impact and migration strategy to avoid disruption
  • Technical debt and architectural limitations of the older system
  • Incremental delivery and risk mitigation (e.g., strangler pattern)
  • Data migration and backward compatibility
  • Long-term scalability and alignment with company strategy

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.