Design a Surge-Capacity Auto-Scaling System
Last updated: October 30, 2025
Quick Overview
Design an auto-scaling system that handles Intuit's predictable seasonal traffic patterns, where TurboTax traffic spikes 10x during tax season and drops dramatically afterward.
Intuit
System Design
Software Engineer
Intuit
October 30, 2025Software Engineer
Onsite - System Design
System Design
Medium
15
8
2,229 solved
Design an auto-scaling system that handles Intuit's predictable seasonal traffic patterns, where TurboTax traffic spikes 10x during tax season and drops dramatically afterward.
Unique to Intuit's seasonal business model. Tests understanding of predictive scaling, cost optimization, and capacity planning for known traffic patterns.
What the Interviewer Expects
- Design predictive auto-scaling that pre-provisions capacity based on historical tax season patterns
- Implement reactive scaling for unexpected traffic bursts within the seasonal window
- Optimize cloud costs by aggressively scaling down during off-season months
- Design graceful degradation strategies when demand exceeds even scaled capacity
- Cover monitoring, alerting, and capacity planning workflows
Key Topics to Cover
Auto-Scaling
Capacity Planning
Predictive Scaling
Cost Optimization
Graceful Degradation
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 do you handle the April 15 tax deadline day when traffic peaks at the absolute maximum?
- What is your strategy for load testing at 10x scale without affecting production?
- How do you balance cost optimization with readiness for unexpected traffic spikes in off-season?
- How would you handle a scenario where a cloud provider region goes down during peak tax season?
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Practice System Design ProblemsSample Answer
Requirements
- Functional Requirements:
- Predictive auto-scaling based on historical traffic data and tax season patterns.
- Reactive scaling to accommodate unexpected traffic spikes during the tax season...
Capacity Estimation
- User Estimation: Assume TurboTax serves approximately 10 million users during tax season.
- Traffic Pattern: If traffic spikes by 10x, daily active users could be 1 million, with peak requ...
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