Anthropic·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say

Apr 2026

Summary

Coding round at Anthropic for a software engineer role, one question but it had enough depth to keep me busy for a while. The edge case handling was where things got tricky.

Questions Asked (1)

Implement a transfer function and an accept-transfer function for accounts. When a transfer is initiated, the source account should hold the funds. Also handle the case where a timeout occurs and a subsequent deposit should cancel the pending transfer.

System DesignAlgorithms & Data StructuresTechnical Trade-offs

Author's notes

Got the basic transfer and accept parts down fine, but that timeout edge case wrecked me.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and defining the state machine for transfers (pending, completed, cancelled, failed). Then design the data model and API contracts, focusing on atomicity, idempotency, and timeout handling. Finally, discuss trade-offs and edge cases like concurrent deposits and distributed transactions.

Pro tip: Emphasize idempotency and exactly-once semantics: use unique transaction IDs and idempotency keys to prevent duplicate transfers or deposits. Also, consider using a saga pattern or two-phase commit for distributed consistency.

1. Clarify Requirements and Constraints

Ask about consistency requirements (strong vs eventual), expected scale, and failure modes. Confirm that a deposit during a pending transfer should cancel it and release held funds.

2. Define State Machine and Data Model

Outline states: pending, completed, cancelled, failed. Design tables/collections for accounts, transfers, and holds, including fields like transfer_id, status, amount, timestamps, and idempotency keys.

3. Design Transfer and Accept-Transfer APIs

Specify endpoints: initiate transfer (creates pending transfer, holds funds) and accept transfer (completes transfer, moves funds). Include idempotency and validation.

4. Handle Timeout and Deposit Cancellation

Implement a timeout mechanism (e.g., scheduled job or TTL) to cancel pending transfers. On deposit, check for pending transfers and cancel them, releasing holds.

5. Discuss Trade-offs and Edge Cases

Cover concurrency control (locks, optimistic locking), distributed transactions (saga, 2PC), idempotency, and failure recovery. Mention monitoring and alerting.

Key Points to Mention

Idempotency: use unique transaction IDs and idempotency keys to ensure operations can be safely retried.
Atomicity: ensure that holding funds and updating transfer status happen atomically, using database transactions or distributed locks.
Timeout handling: use a scheduler or TTL-based expiration to automatically cancel pending transfers after a timeout.
Deposit cancellation: on deposit, check for pending transfers and cancel them, releasing held funds back to the source account.
Concurrency: handle race conditions between transfer initiation, acceptance, timeout, and deposit using locking or optimistic concurrency control.
Distributed consistency: if accounts are in different services/databases, use saga pattern or two-phase commit to maintain consistency.

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