# Design a media DRM and licensing service: system design interview question

> Playback licenses: subscription changes, device limits, country checks, and media key protection during failures.

Source: https://sysround.com/questions/design-media-drm-and-licensing-service
Updated: 2026-11-05


Difficulty: hard. Levels: Senior, Staff+.

## How the interviewer opens it

"Design a service that issues playback licenses for encrypted media. It must enforce subscription, device, and country restrictions without making playback startup unreliable."

## What to clarify first

- Traffic and read:write mix
- Latency and availability
- Subscription and country rules
- Device rules
- License lifetime
- Change deadline
- Billing freshness contract
- DRM boundary
- Data size and durability
- Deployment and scope

## Scope of a strong answer

Core requirements:

- Issue and renew DRM licenses for encrypted titles.
- Check the subscription and the allowed countries.
- Register application installations and enforce the device limit.
- Reflect subscription changes and device revocations in new grants within five minutes.

Usually out of scope:

- Encode, encrypt, or deliver media.
- Build a DRM client or new cryptography.
- Build account login or payment collection.
- Support offline playback or concurrent stream limits.
- Prevent every VPN bypass or screen capture.

## What interviewers probe

### Access changes and service failures

The deadline starts when the source changes. The policy database can respond while it still lacks recent subscription changes.

### Devices and country checks

A client can alter its device claims and country headers. Simultaneous registrations can exceed the account limit.

### Media keys and license contents

A valid account must receive only the keys for authorized content. A key leak can expose the media beyond one account.

### Playback startup under load

License delays block playback startup. Shared dependencies and client retries can turn a small failure into a broad outage.

## Common mistakes

- The candidate treats DRM as a signed URL or an ordinary response that contains a clear media key.
- The service trusts device and country claims from the client.
- The service checks the subscription only at account login.
- The service starts the change deadline at event receipt instead of the source commit.
- The service uses old policy indefinitely to preserve availability.
- The candidate promises immediate revocation while clients hold valid licenses.

## The bar by level

- **Senior:** Enforces device limits atomically. Enforces the source-based deadline through billing, replication, and caches. Separates policy freshness from license expiry. Handles duplicate events, retries, and dependency failures. Sizes each region for failover.
- **Staff+:** Defines source completeness and trust boundaries. Proves the deadline during delayed delivery and source outages. Resolves regional ownership and durability during failure. Quantifies revocation limits and key exposure. Explains when availability must yield to access control.

Practice this question with an AI interviewer: https://sysround.com/practice/new?problem=digital-rights-management


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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.