# Design an e-book platform like Kindle: system design interview question

> E-book delivery and offline sync, with conflicting changes across devices and stable locations for notes and highlights.

Source: https://sysround.com/questions/design-e-book-platform-like-kindle
Updated: 2026-11-05


Difficulty: hard. Levels: Senior, Staff+.

## How the interviewer opens it

"Design an e-book platform that lets users download books and read across devices. Users can change reading positions, notes, and highlights while offline."

## What to clarify first

- Scale
- Read and write mix
- Latency
- Offline use and durability
- Consistency and availability
- Reading positions
- Conflicting notes and highlights
- Book format and editions
- Access and exclusions
- Retention

## Scope of a strong answer

Core requirements:

- Download books for offline use after an access check
- Sync reading positions across devices
- Create, edit, and delete notes and highlights while offline
- Reconcile changes without silently losing note text

Usually out of scope:

- Book purchases and payments
- Publisher uploads and file conversion
- DRM and immediate access revocation
- Shared notes and live group edits
- Book recommendations

## What interviewers probe

### Changes after offline use

Offline devices can edit or delete the same note. Retries and expired history must not lose text or restore deleted objects.

### Reading positions across devices

An earlier position can reflect user intent. Arrival order and client clocks cannot reliably identify the desired resume position.

### Notes inside a book

Page layouts vary across devices. Book revisions can move or remove the passage that a highlight identifies.

### Book downloads and access

Downloads must survive interruption and remain usable offline. Access checks must not make every page depend on a server.

## Common mistakes

- The design always uses the greatest page number as the resume position.
- The server trusts client clocks to order edits across devices.
- The server replaces conflicting note text without preserving a recovery copy.
- The server removes deletion records before old devices return.
- The client uses displayed page numbers as permanent highlight anchors.
- The sync service handles every book byte and every local page access.

## The bar by level

- **Senior:** Defines durable local edits, atomic server changes, and duplicate protection. Resolves note conflicts and deletions without silent loss. Handles divergent positions and expired sync cursors.
- **Staff+:** Proves that snapshots, history expiry, and delayed operations preserve correctness. Defines account ownership during regional failure. Quantifies delivery and history costs. Separates product conflict rules from technical order.

Practice this question with an AI interviewer: https://sysround.com/practice/new?problem=ebook-reading-platform


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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.