Anthropic·Software Engineer·Technical Phone Screen·Senior

SeniorPrefer not to say

Jul 2026Remote

Summary

Anthropic software engineer interview with a meaty in-memory banking system design and implementation problem. The kind of question that looks manageable until you're 40 minutes in and realizing you forgot about transfer expiration cascading into merge edge cases.

Questions Asked (1)

Design and implement a full in-memory banking system supporting account creation, deposits, transfers with expiration, transfer acceptance, top outgoing accounts ranking, and account merging.

System DesignAlgorithms & Data StructuresData Modeling

Author's notes

This one is a beast.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then design the data model and API, and finally discuss algorithms for each operation with complexity analysis. Emphasize trade-offs between different data structures and how to handle edge cases like expiration and merging.

Pro tip: Demonstrate foresight by discussing how to handle concurrent operations and persistence, even though it's in-memory, and mention how you'd test the system thoroughly.

1. Clarify Requirements

Ask questions to understand expected scale, concurrency needs, and specific behaviors (e.g., transfer expiration semantics, merge rules).

2. Design Data Model

Define core entities (Account, Transfer) and their relationships, choosing appropriate data structures for efficient lookups and updates.

3. Define API and Operations

Outline methods for account creation, deposit, transfer initiation/acceptance, ranking, and merging, specifying inputs, outputs, and error handling.

4. Implement Algorithms

For each operation, select and explain algorithms (e.g., heap for top accounts, union-find for merging) and analyze time/space complexity.

5. Handle Edge Cases and Optimizations

Discuss expiration handling, concurrency, and potential optimizations like caching or lazy deletion.

Key Points to Mention

Use of appropriate data structures: hash maps for accounts, priority queues for ranking, and timestamps for expiration.
Transfer expiration: how to track and invalidate expired transfers, possibly with a background thread or lazy checking.
Account merging: strategies like union-find or merging balances and transaction histories, ensuring consistency.
Top outgoing accounts: maintaining a heap or sorted structure, and updating efficiently on each transfer.
Concurrency: thread-safety mechanisms (locks, concurrent data structures) if multiple operations occur simultaneously.
Complexity analysis: time and space for each operation, and trade-offs between different approaches.

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