Edge-Side Includes
Server technique that assembles web pages by combining cached fragments at content delivery network edge locations for improved performance.
Definition
Edge-side includes (ESI) enable dynamic content assembly at CDN edge servers by combining cached page fragments with real-time data. This approach reduces server load while maintaining personalization capabilities.
ESI allows different parts of web pages to have different caching strategies, enabling highly cacheable content to serve from edge locations while dynamic elements fetch from origin servers.
Why It Matters
Modern web applications need both performance and personalization. ESI enables aggressive caching strategies without sacrificing dynamic content, improving user experience while reducing infrastructure costs.
E-commerce and content sites can serve personalized experiences at global scale while maintaining fast page loads through strategic fragment caching and assembly.
Examples in Practice
Amazon's product pages use ESI to cache product descriptions and images at edge locations while dynamically inserting personalized recommendations and pricing for each user.
The Guardian newspaper employs ESI to cache article content globally while personalizing navigation, recommendations, and user-specific content for their international audience.
Shopify's merchant stores use ESI to cache product catalogs and store information at edge locations while providing real-time inventory and personalized shopping experiences.