Design a Distributed Crossword Solver
Company: OpenAI
Role: Software Engineer
Category: System Design
Difficulty: hard
Interview Round: Technical Screen
Design an online service that solves crossword-like word puzzles.
A user submits a puzzle description that includes the grid layout, blocked cells, and word constraints such as word length and any fixed letters already known. The system should compute one or more valid solutions and return them to the user.
Explain both:
1. The core solving algorithm.
2. The distributed system design needed to run the computation at scale.
Your design should address:
- How to represent the puzzle and candidate words.
- How to search efficiently for valid solutions.
- How to parallelize the computation across multiple workers.
- How to aggregate partial results.
- What happens if a worker crashes while solving part of the puzzle.
- How users receive results for fast versus long-running jobs.
Quick Answer: This question evaluates proficiency in constraint-solving algorithms and distributed system architecture, including data representation, efficient search strategies, parallelization, fault tolerance, and result aggregation.