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Design Spotify - Low-Level Design | OneNoughtOne

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Design Spotify

Advanced

Design an object-oriented music streaming platform (like Spotify) with an Artist → Album → Song catalogue, user subscriptions (Free/Premium/Family/Student), playlist management (Public/Private/Collaborative with add/remove/reorder), a full-featured music player with queue management, shuffle (Fisher-Yates with current song pinned), repeat modes (Off/One/All), and playback controls (play/pause/next/previous with 3-second restart rule).

The player loads a queue from an album or playlist and supports "add to queue" for inserting a song to play next. Shuffle preserves the currently playing song at index 0 while randomizing the rest, and toggling shuffle off restores the original order. The previous track command restarts the current song if more than 3 seconds have elapsed, otherwise goes to the previous track. Users can like songs, follow artists, and browse recommendations based on listening history.

Core Use Cases

Music catalogue

Add Artists, Albums (with cover art, genre, release date), and Songs (with duration, track number, featured artists)

User registration & subscriptions

Playlist management

Create/edit playlists (Public/Private/Collaborative); add/remove/reorder songs; follow playlists

Music playback

Play song/album/playlist; pause/resume; next/previous track

Queue management

Load queue from album/playlist; add song to play next; maintain playback position

Shuffle & repeat

Toggle shuffle (Fisher-Yates with current song pinned); set repeat mode (Off/One/All)

Library & likes

Like/unlike songs; follow/unfollow artists and users; recently played history

Search across songs, albums, artists, and playlists by keyword

Recommendations

Genre-based recommendations from listening history; top charts; new releases

Constraints

Playlist songs are ordered — reorder moves a song to a specific index
No duplicate songs in a playlist
Shuffle pins the currently playing song at index 0 and shuffles the rest
Previous track: if > 3 seconds into the song, restart it; otherwise go to previous
Repeat ONE replays the current song; Repeat ALL wraps around the queue
Collaborative playlists allow designated collaborators to add/remove songs
Recently played history is capped at 50 entries (deduped, most recent first)

Assumptions

In-memory storage (no database)
Single-threaded (no real-time streaming concurrency)
Audio playback is simulated (state management only, no actual audio)
No DRM or content licensing logic
Single active session per user (no multi-device sync)

In Scope

Artist, Album, Song hierarchy with metadata
User with subscription tiers
Playlist CRUD with visibility and collaboration
Music player with queue, shuffle, repeat
Previous/next with 3-second restart rule
Like/unlike songs and follow artists
Search across all entity types
Simple genre-based recommendation engine
Top charts and new releases
Recently played history

Out of Scope

Actual audio streaming / codec handling
Offline downloads
Podcasts and audiobooks
Social features (activity feed, shared listening)
Ads for free-tier users
Multi-device sync (Spotify Connect)
Lyrics display
Payment and billing

Approach Guide(Click to expand each section)

Before diving into code, clarify the use cases and edge cases. Understanding the problem deeply leads to better class design.

List Core Use Cases

Identify the primary actions users will perform. For a parking lot: park vehicle, exit vehicle, check availability. Each becomes a method.

Identify Actors

Who interacts with the system? Customers, admins, automated systems? Each actor type may need different interfaces.

Clarify Constraints

What are the limits? Max vehicles, supported vehicle types, payment methods. Constraints drive your data structures.

Ask About Edge Cases

What happens on overflow? Concurrent access? Payment failures? Thinking about edge cases reveals hidden complexity.

Follow-up Questions(Questions an interviewer might ask)

💡 Draw UML class diagrams, sequence diagrams, or any design visualizations. Submit from the Code tab.

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00:00:00

Design Spotify

Advanced

Core Use Cases

Music catalogue

Add Artists, Albums (with cover art, genre, release date), and Songs (with duration, track number, featured artists)

User registration & subscriptions

Playlist management

Create/edit playlists (Public/Private/Collaborative); add/remove/reorder songs; follow playlists

Music playback

Play song/album/playlist; pause/resume; next/previous track

Queue management

Load queue from album/playlist; add song to play next; maintain playback position

Shuffle & repeat

Toggle shuffle (Fisher-Yates with current song pinned); set repeat mode (Off/One/All)

Library & likes

Like/unlike songs; follow/unfollow artists and users; recently played history

Search across songs, albums, artists, and playlists by keyword

Recommendations

Genre-based recommendations from listening history; top charts; new releases

Constraints

Playlist songs are ordered — reorder moves a song to a specific index
No duplicate songs in a playlist
Shuffle pins the currently playing song at index 0 and shuffles the rest
Previous track: if > 3 seconds into the song, restart it; otherwise go to previous
Repeat ONE replays the current song; Repeat ALL wraps around the queue
Collaborative playlists allow designated collaborators to add/remove songs
Recently played history is capped at 50 entries (deduped, most recent first)

Assumptions

In-memory storage (no database)
Single-threaded (no real-time streaming concurrency)
Audio playback is simulated (state management only, no actual audio)
No DRM or content licensing logic
Single active session per user (no multi-device sync)

In Scope

Artist, Album, Song hierarchy with metadata
User with subscription tiers
Playlist CRUD with visibility and collaboration
Music player with queue, shuffle, repeat
Previous/next with 3-second restart rule
Like/unlike songs and follow artists
Search across all entity types
Simple genre-based recommendation engine
Top charts and new releases
Recently played history

Out of Scope

Actual audio streaming / codec handling
Offline downloads
Podcasts and audiobooks
Social features (activity feed, shared listening)
Ads for free-tier users
Multi-device sync (Spotify Connect)
Lyrics display
Payment and billing

Approach Guide(Click to expand each section)

Before diving into code, clarify the use cases and edge cases. Understanding the problem deeply leads to better class design.

List Core Use Cases

Identify the primary actions users will perform. For a parking lot: park vehicle, exit vehicle, check availability. Each becomes a method.

Identify Actors

Who interacts with the system? Customers, admins, automated systems? Each actor type may need different interfaces.

Clarify Constraints

What are the limits? Max vehicles, supported vehicle types, payment methods. Constraints drive your data structures.

Ask About Edge Cases

What happens on overflow? Concurrent access? Payment failures? Thinking about edge cases reveals hidden complexity.

Follow-up Questions(Questions an interviewer might ask)

💡 Draw UML class diagrams, sequence diagrams, or any design visualizations. Submit from the Code tab.

Loading canvas...

Design Spotify

Core Use Cases

Constraints

Assumptions

In Scope

Out of Scope

Approach Guide(Click to expand each section)

Follow-up Questions(Questions an interviewer might ask)

Explore the full editorial.

Sign in to view submissions

Design Spotify

Core Use Cases

Constraints

Assumptions

In Scope

Out of Scope

Approach Guide(Click to expand each section)

Follow-up Questions(Questions an interviewer might ask)

Explore the full editorial.

Sign in to view submissions

Design Spotify

Core Use Cases

Constraints

Assumptions

In Scope

Out of Scope

Approach Guide(Click to expand each section)

Gather Requirements~3 min

Identify Classes & Entities~4 min

Define Relationships~3 min

Apply Design Patterns~4 min

Apply SOLID Principles~3 min

Code Organization~2 min

Follow-up Questions(Questions an interviewer might ask)

1How would you implement Spotify Connect (multi-device playback control)?

2How would you build a collaborative filtering recommendation engine?

3How would you add ad-supported free tier with ad insertion?

4How would you implement offline mode with download management?

5How would you add social features like shared listening (Group Session)?

Key Topics

Asked At

Explore the full editorial.

Sign in to view submissions

Design Spotify

Core Use Cases

Constraints

Assumptions

In Scope

Out of Scope

Approach Guide(Click to expand each section)

Gather Requirements~3 min

Identify Classes & Entities~4 min

Define Relationships~3 min

Apply Design Patterns~4 min

Apply SOLID Principles~3 min

Code Organization~2 min

Follow-up Questions(Questions an interviewer might ask)

1How would you implement Spotify Connect (multi-device playback control)?

2How would you build a collaborative filtering recommendation engine?

3How would you add ad-supported free tier with ad insertion?

4How would you implement offline mode with download management?

5How would you add social features like shared listening (Group Session)?

Key Topics

Asked At

Explore the full editorial.

Sign in to view submissions