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Waymo·Mobile Engineer·Technical Phone Screen·Intermediate

IntermediateRejected
May 2026

Summary

Did a first round for a Mobile Engineer role at Waymo. They had me open Android Studio live and build a pickup screen using Jetpack Compose. Answered everything they asked but still didn't move forward, which was frustrating.

Questions Asked (1)

Q1

Build a Waymo ride pickup screen in Jetpack Compose, incorporating a list view, live data updates, and currency conversion.

System DesignTechnical Trade-offsAPI & Integrations
Author's notes

Pretty involved for a first round.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then outline a high-level architecture that separates UI, data, and domain layers. Focus on how you would implement the list with live updates using Flow and Compose, and handle currency conversion with proper caching and error handling. Emphasize trade-offs and testability.

Pro tip: Demonstrate awareness of real-time data challenges like race conditions and stale data by proposing a single source of truth with unidirectional data flow. Also, mention how you would handle currency conversion rates that update frequently without causing UI jank.

1. Clarify Requirements and Constraints

Ask questions to understand the scope: What data is displayed? How often does it update? What currencies need conversion? Are there offline requirements? This shows you think before coding.

2. Design the Architecture

Propose a layered architecture: UI (Compose), ViewModel, Repository, and data sources (local/remote). Use Kotlin Flow for reactive streams and define a clear data model.

3. Implement the UI with Compose

Describe the composable structure: a LazyColumn for the list, state hoisting, and how to observe live data using collectAsStateWithLifecycle. Mention handling loading, error, and empty states.

4. Handle Live Data Updates

Explain how you would use Flow to emit updates from the repository, possibly combining multiple sources (e.g., ride data and currency rates). Discuss backpressure and lifecycle awareness.

5. Implement Currency Conversion

Outline a strategy for currency conversion: fetch rates from an API, cache them with expiry, and convert amounts in the domain layer. Consider using a dedicated converter class and handling rounding.

Key Points to Mention

  • Use of Kotlin Flow and StateFlow for reactive, lifecycle-aware data streams.
  • LazyColumn for efficient list rendering with keys for stable item identity.
  • Separation of concerns: UI, ViewModel, Repository, and data sources.
  • Currency conversion: caching strategies, error handling, and avoiding UI thread blocking.
  • Handling configuration changes and process death with SavedStateHandle.
  • Testing strategy: unit tests for ViewModel and repository, UI tests for Compose.

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