Design Image Processing Infrastructure for mobile apps

Last updated: February 13, 2026

Quick Overview

Design a event-driven image processing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Zscaler
System Design
Software Engineer
Zscaler
February 13, 2026
Software Engineer
System Design Round
System Design
Hard

44

5

813 solved


Design a event-driven image processing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

ML system design at Zscaler goes beyond model selection. This System Design Round question evaluates your ability to design end-to-end ML pipelines, from data collection to model serving, while considering production constraints like latency and reliability.

What the Interviewer Expects
  • Design the full ML lifecycle from data collection to model monitoring
  • Address cold start, exploration/exploitation, and model freshness
  • Discuss multi-objective optimization and ranking systems
  • Plan for model debugging, fairness, and bias mitigation
  • Design the feature store and training pipeline for scale
  • Address model versioning, canary deployments, and rollback strategies
  • Discuss the data flywheel and long-term system evolution
Key Topics to Cover
Data collection and labeling strategy
Training pipeline and infrastructure
Model serving and latency optimization
A/B testing and experimentation
Feature engineering and feature stores
Online vs offline evaluation
How to Approach This
  1. Start by clarifying functional and non-functional requirements with the interviewer.
  2. Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
  3. Draw a high-level architecture first, then deep dive into 1-2 critical components.
  4. Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
  5. Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
  • How would you debug a model that works well offline but poorly online?
  • How would you handle a 10x increase in prediction requests?
  • How would you handle the cold start problem?
  • What is your model retraining strategy?
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Sample Answer
Requirements

Functional Requirements

  1. Image Upload: Mobile apps must allow users to upload images for processing.
  2. Image Processing: Support various image transformation operations (e.g., resiz...
Capacity Estimation

Back-of-Envelope Calculations

  • Daily Requests: Assume 10 million image processing requests per day.
  • Per-Second Throughput: 10 million requests / 86,400 seconds = ~116 requests per s...

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