Design Image Processing Infrastructure for mobile apps
Last updated: May 25, 2026
Quick Overview
Design a real-time image processing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
PlanetScale
System Design
Software Engineer
PlanetScale
May 25, 2026Software Engineer
Technical Screen
System Design
Medium
4
12
4,850 solved
Design a real-time image processing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
PlanetScale asks this during the Technical Screen to assess your architectural thinking. They want to see how you decompose a complex problem, choose appropriate technologies, and reason about failure modes. Strong candidates proactively discuss monitoring, alerting, and operational concerns.
What the Interviewer Expects
- Systematically gather requirements and estimate capacity (QPS, storage, bandwidth)
- Design a scalable architecture with clear component responsibilities
- Make well-reasoned database and caching decisions with trade-off analysis
- Address consistency vs availability trade-offs specific to the use case
- Discuss partitioning strategy, replication, and data modeling
- Cover failure handling, monitoring, and alerting strategies
Key Topics to Cover
Security and authentication
Caching strategies (local, distributed, CDN)
Requirements gathering and capacity estimation
High-level architecture and component design
Monitoring, logging, and alerting
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 optimize costs as the system scales?
- What would the deployment pipeline look like for this system?
- How would you handle schema migrations with zero downtime?
- How would you implement rate limiting to protect the system?
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Requirements
- Functional Requirements:
- The system must process and return images in real-time for mobile apps with a latency of under 200ms.
- Support image transformations such as resizing, cropping, f...
Capacity Estimation
- Back-of-Envelope Calculations:
- Assume an average image size of 300 KB and each processed image generates an additional 100 KB of metadata.
- For 10,000 QPS, the bandwidth requirement would...
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