Design a cloud file sync service

Q: Design a cloud file sync service

This question evaluates a candidate's expertise in designing large-scale distributed storage and synchronization systems, encompassing metadata and object storage architecture, change notification and sync protocols, deduplication, versioning, conflict resolution, security, and offline reconciliation.

Q: How do I approach System Design interview questions?

System Design questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master system design interviews.

Q: What difficulty level is this interview question?

This is a hard difficulty System Design question, commonly asked during Onsite rounds at Meta.

Q: What role is this question designed for?

This question is commonly asked for Software Engineer candidates at Meta during technical interviews.

Question

System Design: Cloud File Storage and Synchronization Service

Design a Dropbox-like cloud storage and sync service that supports:

Client-side folder monitoring
Chunked uploads/downloads
Deduplication
Versioning
Conflict resolution
Sharing and permissions
Cross-device synchronization

Your design should outline the following components and considerations:

Core Services

Metadata service (namespaces, file/folder entries, versions, ACLs)
Object storage (content-addressed chunks, multi-part uploads)
Change notification (to drive near real-time sync)
Client sync protocol (delta discovery, resumable transfers, conflict detection)
Security: encryption at rest and in transit
Offline support (local state and reconciliation)

System Qualities to Discuss

Consistency model and user-visible semantics
Scaling strategies (storage, metadata, throughput, hot keys)
Bandwidth optimization (dedupe, delta sync, compression, CDN)
Disaster recovery (backups, multi-region replication, failover)

Make reasonable assumptions about scale if needed and state them explicitly.

Design a cloud file sync service

Quick Overview

System Design: Cloud File Storage and Synchronization Service

Core Services

System Qualities to Discuss

Solution

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