# Design Spotify: system design interview question

> Millions of listeners need fast, reliable audio despite network changes and concurrent updates to personal libraries.

Source: https://sysround.com/questions/design-spotify
Updated: 2026-11-05


Difficulty: hard. Levels: Senior, Staff+.

## How the interviewer opens it

"Design a music service with a large song catalog and personal libraries. The service must deliver reliable playback with little delay for millions of listeners."

## What to clarify first

- Catalog and libraries
- Peak traffic and read:write ratio
- Audio formats
- Playback targets
- API latency and consistency
- Availability and durability
- Content source
- Subscription and track removal
- Library behavior
- Scope limits

## Scope of a strong answer

Core requirements:

- Find tracks by title or artist
- Add, remove, and list saved tracks
- Play, pause, and seek within a track

Usually out of scope:

- Music recommendations
- Offline playback
- Ads and billing
- Full DRM
- A portal for artists

## What interviewers probe

### Playback start and seek

Listeners need a fast start, smooth audio, and quick seeks despite changes in network speed.

### A new release at peak load

A popular release can receive millions of requests at once. Most other tracks receive few requests.

### Library changes across devices

Retries and concurrent changes must not create duplicate saved tracks. A later read must include completed writes despite replica lag.

### Track access and removal

Listeners can retain old audio links after an access check. Track removal must stop new fetches within five minutes.

## Common mistakes

- The design treats metadata requests and audio delivery as the same load.
- Application servers carry all audio bytes.
- The player downloads a whole track before playback starts.
- The library permits duplicate saved tracks after retries.
- The service checks access only on a cache miss.
- The design promises to erase audio that clients already fetched.

## The bar by level

- **Senior:** Calculates audio bandwidth and segment request rates. Explains buffer behavior, bitrate choice, and origin protection. Preserves library consistency across retries and failover. Meets the five-minute removal limit.
- **Staff+:** Defines measurable startup and recovery budgets across the player, APIs, and audio path. Handles popular releases and origin failures without excess retries. Quantifies cost and capacity trade-offs. Bounds access expiry and removal lag under failures.

Practice this question with an AI interviewer: https://sysround.com/practice/new?problem=music-streaming


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SysRound (https://sysround.com) is an AI practice tool for system design interviews. It has a voice or typed AI interviewer and a shared whiteboard. At the end, you get feedback on each skill and a model answer. The AI feedback can be wrong.