Circle·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say

Jun 2026Remote

Summary

Circle SWE coding round, one question the whole session. Felt manageable at first but the edge cases piled up fast and I left unsure if I'd covered everything.

Questions Asked (1)

Design and implement an in-memory RecipeStore class with create, get, update, and delete operations. IDs are assigned sequentially. Recipe names must be unique in a case-insensitive way, but stored casing should be preserved. Updates can only change casing of the name, not the name itself, and the recipeId must match the updated recipe's id.

Algorithms & Data StructuresSystem DesignData Modeling

Author's notes

I started with a plain dictionary keyed by integer ID and thought I was done in ten minutes.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and edge cases, then outline the data structures: a map for id-to-recipe and a map for case-insensitive name-to-id. Implement each operation with careful validation, especially for uniqueness and update constraints, and discuss time/space complexity.

Pro tip: Mention that you would normalize names using a consistent case-folding method (e.g., toLowerCase with locale consideration) and store the original casing separately. Also, highlight that updates must validate the recipeId matches and that name changes are only allowed for casing.

1. Clarify Requirements and Edge Cases

Ask questions to confirm: ID assignment (sequential starting from 1?), behavior on duplicate names (case-insensitive), update rules (only casing changes, ID must match), and error handling (exceptions vs. null).

2. Design Data Structures

Use a hash map for O(1) access by ID (id -> Recipe) and another hash map for name uniqueness (normalized name -> id). Consider thread-safety if needed.

3. Implement CRUD Operations

For create: validate name uniqueness, assign next ID, store in both maps. For get: retrieve by ID. For update: validate ID match, check if name change is only casing, update maps accordingly. For delete: remove from both maps.

4. Handle Edge Cases and Errors

Define behavior for non-existent IDs, duplicate names, invalid updates (e.g., changing name beyond casing), and ensure atomicity of operations.

5. Analyze Complexity and Test

State time and space complexity (O(1) average for operations, O(n) space). Walk through test cases: create, duplicate name, update casing, update invalid, delete, get after delete.

Key Points to Mention

Case-insensitive uniqueness: normalize names (e.g., toLowerCase) for comparison while preserving original casing.
Sequential ID assignment: maintain a counter, increment on each create.
Update constraints: recipeId must match the existing recipe's id; name can only change in casing, not content.
Data structures: two hash maps for efficient lookups and uniqueness checks.
Error handling: throw exceptions or return error codes for invalid operations.
Complexity: O(1) average time for CRUD operations, O(n) space.

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