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Anthropic·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Apr 2026

Summary

Interviewed for a software engineering role at Anthropic and got a coding question around basic banking operations. Pretty straightforward on the surface but there's more to think about than it first seems.

Questions Asked (1)

Q1

Implement a create account function and a deposit function for a simple banking system.

Algorithms & Data StructuresTechnical Trade-offsSystem Design
Author's notes

Seemed easy at first and that's probably where I tripped up a little.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints (e.g., concurrency, persistence, error handling) before writing any code. Then design a clean, testable API with proper validation and atomic operations, and implement it with attention to edge cases and thread safety. Finally, discuss trade-offs and potential extensions.

Pro tip: Demonstrate production-readiness by addressing concurrency and idempotency upfront—e.g., using locks or optimistic concurrency control—and mention how you'd test for race conditions. This shows you think beyond happy-path coding.

1. Clarify Requirements

Ask about expected scale, concurrency, persistence, error handling, and whether accounts can go negative. Confirm the API shape (e.g., function signatures, return types).

2. Design the Data Model and API

Define an Account class/struct with fields like id, balance, and owner. Specify createAccount and deposit methods with clear input validation and error returns.

3. Implement with Safety and Correctness

Write code that validates inputs, handles errors gracefully, and ensures atomic deposits (e.g., using locks or transactions). Consider idempotency for deposits.

4. Test and Discuss Trade-offs

Outline unit tests for edge cases (negative amounts, duplicate IDs, concurrent deposits). Discuss trade-offs like in-memory vs. persistent storage, locking granularity, and scalability.

Key Points to Mention

  • Input validation (e.g., non-negative deposit amount, unique account ID)
  • Concurrency control (e.g., mutex, optimistic locking) to prevent race conditions
  • Error handling and return types (e.g., exceptions vs. result objects)
  • Idempotency of deposit operations (e.g., using request IDs)
  • Persistence and durability considerations (e.g., database transactions)
  • Testing strategy including unit tests and concurrency tests

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