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Waymo·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Phone screen for a software engineer role at Waymo. The technical portion was an object-oriented design problem built around a real-ish business scenario, and the interviewer seemed way more interested in how I was thinking through the problem than whether I got to a clean solution fast.

Questions Asked (1)

Q1

Design a class that processes two types of timestamp-based signals and returns continuous time intervals satisfying certain conditions.

System DesignAlgorithms & Data StructuresData Modeling
Author's notes

The problem sounds manageable until you realize there are a bunch of edge cases around how the two signal types interact near interval boundaries.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem: define the two signal types, the conditions for valid intervals, and the expected output format. Then outline a class design that ingests signals, maintains state, and computes continuous intervals using an event-driven or sweep-line approach. Discuss trade-offs between different data structures and algorithms, and consider edge cases and scalability.

Pro tip: Demonstrate awareness of real-world constraints like out-of-order signals, clock skew, and memory limits, and propose a streaming solution that handles them. Also, mention how you would test the class with unit tests covering edge cases.

1. Clarify Requirements

Ask questions to understand the signal types, the conditions for intervals, and the expected output. Confirm whether signals arrive in order, if intervals can overlap, and the required time/space complexity.

2. Define Data Model

Design classes or structs to represent signals and intervals. Decide on the internal state needed to track active intervals and signal history.

3. Choose Algorithm

Select an approach such as sweep-line, event-driven, or interval merging. Explain how it processes signals to produce continuous intervals satisfying the conditions.

4. Handle Edge Cases

Address scenarios like out-of-order signals, simultaneous events, empty inputs, and overlapping intervals. Describe how the design ensures correctness.

5. Analyze and Optimize

Discuss time and space complexity, and propose optimizations for scalability, such as streaming or incremental processing.

Key Points to Mention

  • Event-driven or sweep-line algorithm for processing timestamped signals
  • Data structures like priority queues, balanced trees, or interval trees for efficient querying
  • Handling out-of-order signals and clock skew
  • Interval merging and continuity conditions
  • Time and space complexity analysis
  • Testing strategy including unit tests and edge cases

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