Varnish Cache

Varnish Cache is a high-performance HTTP accelerator commonly deployed in front of web servers to cache content and reduce backend load and latency. It operates as a reverse proxy and is tuned for high throughput, with flexible request handling and caching behavior.

Key Features

• HTTP reverse proxy caching to speed up websites and APIs
• Flexible request routing and cache logic via VCL (Varnish Configuration Language)
• Advanced cache controls (TTL, grace/saint modes, cache invalidation patterns)
• Detailed shared-memory logging (VSL) and runtime metrics for troubleshooting
• Supports cache purging/ban mechanisms to invalidate cached objects
• Designed for performance and efficient resource usage under heavy traffic

Use Cases

• Accelerating content-heavy sites and CMS-backed pages by caching responses
• Protecting origin servers from traffic spikes and reducing infrastructure cost
• Serving as an edge caching layer in front of load balancers or web servers

Limitations and Considerations

• Primarily targets HTTP caching; it is not a general-purpose L4 load balancer
• Effective configuration often requires understanding VCL and HTTP caching semantics

Varnish Cache is a mature, widely used choice for organizations that need fast HTTP caching and fine-grained control over request handling. It fits well as an edge or mid-tier caching layer where performance and observability are critical.