Caching Server

A caching server, also known as a cache server, is a type of server that stores copies of frequently accessed or requested data, known as cached content. The purpose of a caching server is to reduce latency, improve response times, and minimize the load on upstream servers by serving cached content instead of fetching it from the original source every time a request is made.

Caching servers implement a caching mechanism to store copies of data, such as web pages, images, scripts, or other resources. Cached content is stored temporarily and can be quickly served to users upon subsequent requests.

Caching servers prioritize caching frequently accessed content to optimize performance for users. Caching servers follow HTTP Protocol caching headers provided by web servers and applications to determine how long to store cached content and when to revalidate it. Common HTTP caching headers include Cache-Control, Expires, Last-Modified, and ETag.

Types of Caching Servers:

  • Web Proxy Caches: These caches are often deployed at the network edge, acting as intermediaries between clients and web servers. They store copies of content requested by clients and serve it locally.
  • Content Delivery Network (CDN) Caches: Content Delivery Network consist of distributed caching servers strategically located around the globe. They cache and deliver static assets (e.g., images, stylesheets) to users based on their geographical location.
  • Reverse Proxy Caches: Placed in front of web servers, reverse proxy caches store copies of dynamic content generated by web applications. They help offload server processing and improve response times.
  • Browser Caches: While not traditional caching servers, web browsers maintain local caches on users' devices to store copies of recently visited web pages and resources.

Caching servers implement cache invalidation mechanisms to ensure that stale or outdated content is periodically purged from the cache. Techniques for cache invalidation include time-based expiration, versioning, and cache purging.

Some caching servers also function as Load Balancers, distributing incoming requests across multiple backend servers to optimize resource utilization.