Design a File Storage for Plaid
Last updated: May 31, 2026
Quick Overview
Design a event-driven file storage system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Plaid
System Design
Software Engineer
Plaid
May 31, 2026Software Engineer
Onsite
System Design
Hard
35
11
3,210 solved
Design a event-driven file storage system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Plaid typically last 45-60 minutes. You are expected to drive the conversation, starting from requirements gathering through to a detailed architecture. The interviewer will evaluate your ability to handle ambiguity and make practical engineering decisions.
What the Interviewer Expects
- Drive the design discussion proactively with minimal interviewer guidance
- Perform detailed capacity estimation and use it to inform design decisions
- Design for global scale with multi-region deployment and data consistency
- Deep dive into 2-3 critical components with implementation-level detail
- Address complex trade-offs: CAP theorem, eventual consistency, conflict resolution
- Discuss operational excellence: deployment strategy, chaos engineering, SLOs/SLIs
- Propose a phased rollout plan from MVP to full-scale system
Key Topics to Cover
Database selection and data modeling
Monitoring, logging, and alerting
Load balancing and horizontal scaling
Message queues and async processing
How to Approach This
- Start by clarifying functional and non-functional requirements with the interviewer.
- Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
- Draw a high-level architecture first, then deep dive into 1-2 critical components.
- Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
- Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
- How would you handle a region-wide outage?
- How would you handle schema migrations with zero downtime?
- What would the deployment pipeline look like for this system?
- How would you optimize costs as the system scales?
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Requirements
- Functional Requirements:
- Store and retrieve files associated with financial transactions securely.
- Support event-driven architecture to process file uploads and downloads asynchron...
Capacity Estimation
- User Base: Assuming 1 million active users.
- File Requests: Each user uploads and retrieves an average of 10 files per day.
- Total Daily Requests: 1 million users * 10 requests = 1...
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