Design an object store with deduplication
Overview
This question evaluates a candidate's ability to design scalable, durable object storage systems with deduplication, touching on storage architecture, data modeling, metadata management, consistency, and garbage collection.
Snowflake
Dec 15, 2025, 12:00 AM
Software Engineer
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System Design
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System Design Prompt
Design a simplified cloud object storage service (similar to an object store) that allows users to upload and download files.
The key focus is reducing cost by avoiding storing duplicate files (deduplication).
Core Requirements
- Upload a file (binary blob) and store it durably.
- Download a previously uploaded file by an identifier.
- Support basic metadata (filename, content-type, size, upload time, owner).
- Avoid saving duplicates: if multiple users upload the exact same content, store it only once.
Non-Goals (to keep it simpler)
- No complex lifecycle rules, tiering, or CDN features required.
- Permissions can be simplified (assume authenticated users, simple ACL).
Scale / Assumptions (you may choose reasonable numbers)
- Large number of objects; objects can be large (up to multiple GB).
- High read/write throughput.
- Must be resilient to failures.
What to Cover
- APIs
- High-level architecture
- Data model and storage layout
- Deduplication approach (how to detect duplicates, how to reference shared content)
- Consistency and correctness concerns (races, partial uploads)
- Deletion / garbage collection (when shared content can be removed)
- Operational considerations (monitoring, cost trade-offs)
Solution
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