Senior Developer — Service Design & Trade-offs

What this session covers

• Decomposition
• Data ownership
• Consistency
• Contracts
• Scaling

Questions you'll face

1. 1. Describe a piece of code you owned that became hard to change. What made it hard, and how did you address it?

   ~3 min

   Looks for concrete design judgement rather than textbook principles.

2. 2. You are designing a REST or RPC API for a resource other teams will consume for years. What decisions do you make on day one and why?

   ~3 min

   Checks interface thinking: versioning, pagination, errors, idempotency.

3. 3. Where do you draw the line between unit, integration and end-to-end tests on a service you own?

   ~3 min

   Tests pragmatic testing strategy and cost awareness.

4. 4. A request that should take 80ms is taking 2 seconds under load. How do you find out why?

   ~3 min

   Assesses systematic debugging under production constraints.

How the time is spent

1. 1

   Warm-up & context · 5 min

   Interviewer intro, your background, how the session runs.

2. 2

   Core questions · 27 min

   Role-specific questions with live follow-ups based on your answers.

3. 3

   Deep dive · 9 min

   One topic explored to the edge of your experience.

4. 4

   Your questions & wrap · 5 min

   Close the loop and hand over to feedback generation.