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Early-stage Startup·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Apr 2026

Summary

Second part of a technical screen for a software engineering role, came after solving an initial problem. The follow-up threw in server failures, locked doors, and keys you had to collect to proceed. Weirdly fun, actually.

Questions Asked (1)

Q1

Design or implement an endpoint that handles server failures, and models a scenario where a user must collect keys to unlock doors before proceeding.

API & IntegrationsSystem DesignAlgorithms & Data Structures
Author's notes

This was the follow-up after the first problem, and it shifted the whole vibe of the interview.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then design a robust endpoint with failure handling and a key-door model. Implement the core algorithm using graph traversal, and discuss trade-offs and scalability.

Pro tip: Demonstrate awareness of startup constraints by proposing a simple, iterative solution first, then discussing how to evolve it for scale and reliability.

1. Clarify Requirements

Ask questions to understand the scope: expected load, failure modes, consistency needs, and whether the key-door model is part of the API or a separate game logic.

2. Design the API Endpoint

Define the endpoint's purpose, HTTP method, request/response schema, and error handling. Consider idempotency and retry mechanisms for server failures.

3. Model the Key-Door Scenario

Represent the problem as a graph where rooms are nodes and doors are edges. Keys act as prerequisites to traverse certain edges. Use BFS/DFS to determine if all doors can be unlocked.

4. Implement Failure Handling

Incorporate retries with exponential backoff, circuit breakers, and fallback responses. Ensure the endpoint remains available and data consistent during failures.

5. Discuss Trade-offs and Scalability

Talk about time/space complexity, potential bottlenecks, and how to scale horizontally. Mention monitoring and logging for production readiness.

Key Points to Mention

  • Idempotency and retry logic for handling server failures
  • Graph traversal algorithms (BFS/DFS) for key-door dependency resolution
  • Circuit breaker pattern and graceful degradation
  • API design best practices (RESTful, clear error codes, versioning)
  • Concurrency and consistency considerations (e.g., locking, transactions)
  • Monitoring, logging, and alerting for failure detection

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