live-coding-interview-spring-fw

Live Coding Interview Rules (Java + Spring Boot) — General + Simple

North Star

Deliver a working, locally runnable web service with a small, high-quality test suite in a 2-hour live coding interview. Success = predictable behavior + clear structure + explainable decisions.

Hard Simplicity Constraints (Non-Negotiable)

• Keep architecture to 3 layers max:
  • Controller (HTTP) → Service (business rules) → Repository/Store (in-memory)
• Avoid extra patterns unless asked:
  • ❌ hexagonal/ports-adapters
  • ❌ DDD aggregates/repositories/specifications
  • ❌ factories/builders for everything
  • ❌ excessive interfaces
  • ❌ reflection / metaprogramming
  • ❌ complex generics
• Default persistence: in-memory.
• Default concurrency: assume requests can be concurrent → use safe data structures if stateful.
• Keep file count low and names obvious.

First 10 Minutes (How to start)

1. Restate the problem in 3–5 sentences.
2. Ask 2–5 clarifying questions only if needed.
3. List:
   • key entities
   • endpoints
   • edge cases
   • explicit non-goals
4. Create a short README (no code) and then start coding.

Time cap: README must be ≤ 10 minutes.

Delivery Order (Bias to Working Software)

1. Boot app and health-check run
2. Implement one endpoint end-to-end (happy path) + tests
3. Implement the second endpoint + tests
4. Add validation + consistent errors + tests
5. Harden edge cases + minimal refactor
6. Optional extras only if asked (idempotency, filtering, pagination, etc.)

If stuck: prioritize a minimal working slice and test it.

API Behavior Rules

• Return consistent JSON.
• Use standard status codes:
  • 200 OK (GET success)
  • 201 Created (POST create)
  • 400 Bad Request (validation/format)
  • 404 Not Found (missing resource)
  • 409 Conflict (invalid state / duplicate / unexpected step)
• Provide a consistent error response:
  • code (string)
  • message (human-readable)
  • details (optional list, e.g. field errors)
• Use @RestControllerAdvice to centralize error mapping.