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Tradedesk·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Coding round at Tradedesk for a software engineer role. The main problem was designing a recipe management system from scratch, which sounds trivial until you actually have to nail down the error handling and return types on the spot.

Questions Asked (1)

Q1

Design and implement a Recipe Management System that supports adding, updating, and deleting recipes, where each recipe has a unique name, a list of ingredients, and an ordered list of steps. What are the return types and error conditions for duplicate adds and missing names?

System DesignData ModelingTechnical Trade-offs
Author's notes

The core logic wasn't hard but I fumbled the error handling part.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then propose a data model and API design that handles CRUD operations with clear return types and error conditions. Emphasize trade-offs between different data structures and error handling strategies, and discuss how to ensure uniqueness and ordering.

Pro tip: Demonstrate maturity by discussing idempotency and concurrency: e.g., how to handle duplicate adds in a distributed system, and whether updates should be idempotent. Also, consider using a unique identifier separate from the name to allow renaming.

1. Clarify Requirements

Ask about expected scale, persistence needs, and whether names can be changed. Confirm that recipes are uniquely identified by name and that ingredients and steps are ordered.

2. Design Data Model

Propose a Recipe class/struct with fields: name (string, unique), ingredients (list of strings), steps (ordered list of strings). Consider using a map from name to Recipe for O(1) access.

3. Define API and Return Types

For add: return boolean or Result type indicating success/failure. For update: return boolean or updated Recipe. For delete: return boolean. Specify error conditions: duplicate add returns false or throws DuplicateRecipeException; missing name on update/delete returns false or throws RecipeNotFoundException.

4. Handle Error Conditions

Decide on error handling strategy: exceptions vs. return codes. Discuss trade-offs: exceptions for exceptional cases, return codes for expected failures. Ensure duplicate adds are rejected and missing names are handled gracefully.

5. Discuss Trade-offs and Extensions

Talk about concurrency (locking, optimistic concurrency), persistence (database schema with unique constraint on name), and scalability (sharding by name). Mention idempotency and whether operations should be idempotent.

Key Points to Mention

  • Use a map/dictionary keyed by recipe name for O(1) lookup and uniqueness enforcement.
  • Return types: boolean for success/failure, or Result<T> for more detailed error info; consider exceptions for error conditions.
  • Duplicate add: return false or throw DuplicateRecipeException; missing name on update/delete: return false or throw RecipeNotFoundException.
  • Ordered list of steps: use a list (array) to maintain order; ingredients can be a set if order doesn't matter, but question says list so preserve order.
  • Concurrency: use locks or transactions to prevent race conditions on duplicate adds.
  • Persistence: database table with unique constraint on name; handle duplicate key errors.

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