rippling·Software Engineer·Onsite - System Design / Architecture·Senior

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Jun 2026

Summary

Rippling software engineer interview that was basically one big system design question: build a music player from scratch. More involved than I expected, they wanted class hierarchies, state machines, the whole thing.

Questions Asked (1)

Design and implement a music player system covering a song library, playlists, playback controls, playback modes (shuffle, repeat-one, repeat-all, off), and a now-playing queue distinct from playlists. Include class design, key method signatures, the play/pause/next/previous state machine under different mode combinations, and how you'd test edge cases like empty playlists or mid-song mode changes.

System DesignAlgorithms & Data StructuresTechnical Trade-offs

Author's notes

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and defining core entities (Song, Playlist, Queue, Player) with clear responsibilities. Then walk through the state machine for playback controls under different modes, and finally discuss testing strategies for edge cases. Emphasize separation of concerns and extensibility.

Pro tip: Treat the now-playing queue as the single source of truth for playback order, and derive it from the playlist and mode. This simplifies mode changes and avoids inconsistent state.

1. Clarify Requirements and Scope

Ask about expected scale, persistence, user interactions, and whether modes can be combined (e.g., shuffle + repeat). Confirm that the queue is distinct from playlists and can be modified independently.

2. Design Core Classes and Interfaces

Define Song, Playlist, Queue, and Player classes. Specify key methods like play(), pause(), next(), previous(), setMode(), addToQueue(), etc. Explain how the queue is populated from a playlist based on the current mode.

3. Model Playback State Machine

Describe states (Playing, Paused, Stopped) and transitions triggered by play/pause/next/previous. Detail how next/previous behave under each mode: shuffle (random next, history for previous), repeat-one (same song), repeat-all (wrap around), off (stop at ends).

4. Handle Mode Changes and Edge Cases

Explain how changing mode mid-song affects the queue and playback. For example, switching to shuffle should reshuffle remaining songs; switching to repeat-one should loop current song. Address empty playlist, single song, and end-of-queue scenarios.

5. Outline Testing Strategy

Propose unit tests for each mode and transition, integration tests for queue manipulation, and edge case tests (empty playlist, next on last song, mode change during playback). Mention mocking time or randomness for deterministic tests.

Key Points to Mention

Separation of concerns: Player controls playback, Queue manages order, Playlist stores songs.
State machine with clear states and transitions, including how next/previous depend on mode.
Shuffle implementation: maintain a shuffled order and a history stack for previous.
Repeat modes: repeat-one loops current song; repeat-all wraps queue; off stops at boundaries.
Queue as a dynamic structure that can be modified independently of playlists.
Testing edge cases: empty playlist, single song, mode changes mid-song, and boundary conditions.

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