Anthropic·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say

May 2026

Summary

Anthropic coding interview focused on building an in-memory key-value store from scratch. Pretty straightforward scope for this part, no TTL or snapshot stuff yet, just the core operations.

Questions Asked (1)

Design and implement an in-memory database that supports set(key, value), get(key), and delete(key) operations.

System DesignAlgorithms & Data StructuresTechnical Trade-offs

Author's notes

Not as trivial as it sounds once you start thinking about edge cases.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements (e.g., concurrency, persistence, TTL) and then propose a simple hash map-based design, discussing trade-offs. Implement the core operations with attention to edge cases and complexity, and optionally extend to thread-safety or eviction policies.

Pro tip: Demonstrate awareness of real-world concerns like thread safety and memory management, and mention how you'd test the implementation, including edge cases like deleting non-existent keys.

1. Clarify Requirements

Ask about expected scale, concurrency needs, persistence, and any additional features like TTL or eviction policies.

2. Propose Data Structure

Suggest using a hash map (e.g., HashMap in Java, dict in Python) for O(1) average-case operations, and discuss potential collisions and resizing.

3. Implement Core Operations

Write pseudocode or actual code for set, get, and delete, handling edge cases such as missing keys and null values.

4. Discuss Trade-offs and Extensions

Talk about time/space complexity, thread safety (e.g., using locks or concurrent data structures), and optional features like TTL or LRU eviction.

5. Test and Validate

Outline test cases including basic operations, edge cases, and concurrency scenarios if applicable.

Key Points to Mention

Time complexity: O(1) average for set, get, delete with hash map
Handling collisions and resizing in hash map implementation
Thread safety: using locks, concurrent hash maps, or sharding
Memory management: potential memory leaks, eviction policies
Edge cases: deleting non-existent keys, null values, concurrent modifications
Testing strategies: unit tests, stress tests, concurrency tests

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