Design a cloud storage service

Q: Design a cloud storage service

This question evaluates a candidate's competence in designing large-scale cloud document storage and sharing systems, testing knowledge of distributed storage and metadata modeling, API design, consistency and replication strategies, security, and operational concerns.

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 Amazon.

Q: What role is this question designed for?

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

Question

Context

Design the backend for a large-scale cloud document storage and sharing service (similar to Google Drive). Assume web and mobile clients, global user base, multi-AZ within a region to start, with a path to multi-region active-active.

Requirements

Cover the following end-to-end aspects:

Functional requirements

Upload and download files
Folder hierarchy (create/move/rename)
Metadata and search (name, content, tags)
Sharing and ACLs (users, groups, link-based)
Versioning (restore, diff-friendly)
Trash and restore (soft delete, purge after retention)

APIs

REST or gRPC endpoints for core operations
Chunked/resumable upload API
Permission management APIs
Search API

Data model

Items (files/folders), versions, ACLs, shares, activities
Indices to support listing, search, and permission checks

Storage architecture

Object store for blobs
Metadata store for items/ACLs/versions
Indexing/search system for content/name queries

Consistency model

Read-after-write guarantees, eventual for search
Transactional semantics for rename/move/share within a user’s tree

Partitioning and replication

Sharding strategy for metadata and search
Multi-AZ replication; path to multi-region

Upload chunking and resumability

Initiation, part upload, completion, resume after failures

Virus scanning and thumbnails

Asynchronous pipeline post-upload

Security

Encryption in transit and at rest (key management, envelope encryption)
Permission checks (inherited ACLs, link tokens)

Rate limiting and abuse controls
Monitoring and observability
Scalability, availability, and cost considerations
Rough capacity estimates and a high-level diagram

Provide concrete assumptions where needed, and justify key trade-offs.

Design a cloud storage service

Quick Overview

Context

Requirements

Solution

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Design a cloud storage service

Quick Overview