System Design FAQ: Top Questions

An Image Processing Pipeline supports uploading, transforming (resize, crop, watermark), and serving images with CDN support and caching. It should ensure speed, reliability, and dynamic transformations.

📋 Functional Requirements

• Support upload and on-demand transformations
• Expose URL-based transformation API
• Serve images from cache/CDN
• Preserve aspect ratios, optimize formats (WebP, AVIF)

📦 Non-Functional Requirements

• Low latency for popular images
• Parallel processing for heavy transformations
• Scalable, stateless transformation service

🏗️ Architecture

• Uploader: Upload via API → S3/GCS
• Transformer: On-demand service (Lambda, Node.js, Go)
• CDN: Caches transformed output (e.g., CloudFront, Fastly)
• Metadata Store: Stores transformation history and hash

🌐 URL Format for Transformation

https://cdn.example.com/image/12345?w=500&h=300&format=webp&fit=cover
        

🛠️ Example ImageMagick Command

convert input.jpg -resize 500x300^ -gravity center -extent 500x300 -quality 80 -strip output.webp
        

🚀 On-Demand Lambda (Node.js)

const sharp = require('sharp');

exports.handler = async (event) => {
  const { w, h, format } = event.queryStringParameters;
  const inputBuffer = await getImageFromS3("original.jpg");

  const transformed = await sharp(inputBuffer)
    .resize(+w, +h)
    .toFormat(format || 'webp')
    .toBuffer();

  return {
    statusCode: 200,
    headers: { "Content-Type": `image/${format}` },
    body: transformed.toString("base64"),
    isBase64Encoded: true
  };
};
        

🧪 Caching Strategy

• CDN with long TTL + cache-busting via URL hash
• Local LRU disk cache on edge node

🔐 Security Practices

• Signed URLs for write or private access
• Rate limiting on public endpoints

📈 Metrics

• Cold vs hot transformation ratio
• Average image processing time
• CDN cache hit/miss

🧰 Tools and Infra

• Transform: ImageMagick, Sharp, Pillow
• Storage: S3, GCS, local SSD
• CDN: Cloudflare, CloudFront, Fastly

📌 Final Insight

Use stateless transformation backed by S3 and CDN. Optimize for popular image sizes, pre-generate critical formats, and cache aggressively to reduce origin hits and cost.