Varnish Cache

Varnish Cache is a high-performance open-source HTTP caching server and reverse proxy software. Its core focuses on accelerating the caching of static and dynamic content. By storing frequently accessed content in memory, it achieves millisecond-level response times, significantly reducing load on origin servers and network latency.

The project was initiated and maintained by Varnish Software in Norway. Since its release in 2006, it has become a globally leading open-source caching solution, widely deployed across high-traffic websites, CDN nodes, and enterprise-level network architectures. It is renowned for its lightweight, efficient, and customizable features.

1. Varnish Cache Basics

• Service Provider Name: Varnish Cache
• English Name: Varnish Cache
• Established: First released in 2006, continuously maintained by Varnish Software
• Headquarters Address: Oslo, Norway
• Official website address:https://varnish-cache.org
• Service Type: Open-source HTTP/HTTPS caching server, reverse proxy, CDN core component, content acceleration solution
• Reference Pricing: The open-source community edition is completely free. Custom quotes are required for the commercial edition (Varnish Enterprise) and technical support services, with a starting price of approximately $5,000 per year (billed per server node).
• Trial Availability: The open-source community edition is ready to use upon download with no trial restrictions. The commercial edition offers a 30-day free trial (contact sales).

2. Core Advantages and Technical Features of Varnish Cache

Memory-Priority High-Performance Cache
Utilizing memory as the primary caching medium eliminates disk I/O bottlenecks, enabling support for hundreds of thousands of concurrent requests per second. Cache hit rates exceed 90%, with static content response times reduced to millisecond levels, significantly enhancing user access experience.

Flexible VCL Configuration Language
Based on the proprietary Varnish Configuration Language (VCL), it enables developers to customize caching policies, request routing, content rewriting, and other logic. It supports flexible control of caching behavior based on multiple dimensions such as URLs, request headers, and client information, adapting to complex business scenarios.

Modular and Scalable Architecture
Core functionality is implemented through modules, supporting dynamic loading of third-party modules (such as cache compression, WebSocket proxies, monitoring extensions, etc.). It also provides a rich set of API interfaces to facilitate integration with existing operations tools and monitoring systems, meeting the demand for personalized feature expansion.

Comprehensive protocol support and security features
Supports HTTP/1.1, HTTP/2, and HTTPS (requires TLS termination module), meeting modern web application protocol requirements; Includes built-in security mechanisms such as request throttling, cache tamper protection, and IP access control; The commercial edition further provides advanced security features including DDoS protection and WAF integration.

Intelligent Caching Strategy and Expiration Mechanism
Supports multiple cache eviction algorithms (such as LRUI and LFU), dynamically adjusting cache priority based on content popularity; provides precise cache invalidation mechanisms, supporting manual purge, tag-based invalidation, time-window expiration, and other methods to ensure real-time cache content.

3. Varnish Cache Core Products and Services

• Varnish Cache Community Edition: An open-source, free-to-use foundational caching and reverse proxy software offering core caching functionality.
• Varnish Enterprise: Commercial edition solution featuring advanced caching capabilities, security enhancements, dedicated modules, and SLA guarantees.
• Varnish Plus: An enterprise-grade security acceleration suite integrating caching, WAF, and DDoS protection.
• Commercial Technical Support Services: Includes 24/7 technical support, troubleshooting, and configuration optimization guidance.
• Customized Deployment and Training Services: Providing architecture design, deployment implementation, and technical training tailored to enterprise requirements.
• Varnish Controller: A cluster management tool that enables centralized monitoring and configuration management for multi-node Varnish instances.

4. Varnish Cache Supports Regions / Billing Currencies

• Coverage Area: Worldwide, deployable in any region with server infrastructure (e.g., North America, Europe, Asia, Oceania, etc.)

Deployment Flexibility: As open-source software, deployment locations are unrestricted. Users can flexibly deploy nodes based on their business coverage areas. The commercial edition supports global distributed cluster deployment, enabling cross-region content acceleration through intelligent routing.

Supported billing currencies: The open-source community edition is free of charge; commercial editions and services are primarily billed in US dollars (USD), with euro (EUR) and British pound (GBP) settlement available in select regions.

5. How to Integrate Varnish Cache

1. Environment Preparation: Select a compatible Linux distribution (such as Ubuntu, CentOS, or Debian) and configure server resources to meet requirements (recommended minimum RAM: 4GB).
2. Installation and Deployment: Install Varnish Cache Community Edition using the source code package, package manager, or container image (Docker) provided on the official website. For the commercial edition, contact sales to obtain the installation package.
3. Basic Configuration: Create a VCL configuration file to define caching policies (such as cached object types and expiration times), backend server addresses, and request routing rules.
4. Start the service: Launch the Varnish service, configure it to start automatically at boot, and verify the service status using command-line tools.
5. Testing and Validation: Direct client requests to the Varnish server to test metrics such as cache hit rate and response time, then adjust the VCL configuration to optimize performance.
6. Advanced Configuration (Optional): Configure HTTPS support, cache clusters, and monitoring alerts (e.g., integrate with Prometheus and Grafana). The commercial edition enables advanced security features.

6. Varnish Cache Use Cases

• High-traffic e-commerce websites: Cache product detail pages, images, and static resources to reduce pressure on origin servers and enhance peak traffic handling capacity.
• News and Content Portal: Accelerate the distribution of articles, images, video thumbnails, and other content to enhance user reading experiences and reduce page loading times.
• API Services: Cache frequently accessed API response data to reduce backend database load and enhance API interface concurrency processing capabilities.
• CDN Node Deployment: As the core caching component of self-built CDNs, these nodes are deployed at the edge to enable regional content acceleration.
• Corporate Websites and Marketing Sites: Accelerate the loading of static resources (CSS, JS, images) to enhance website performance and SEO metrics.
• SaaS Platform: Provides a unified caching layer for multi-tenant SaaS applications, optimizing resource sharing and access speed.

7. Varnish Cache Frequently Asked Questions

Is Varnish Cache Community Edition completely free?
Yes, the Community Edition follows the BSD license, allowing completely free download, use, and modification with no functional restrictions or usage time limits.

Does Varnish Cache support caching dynamic content?
Support. Through VCL configuration, conditional caching of dynamic content can be achieved (e.g., based on user sessions or request parameter filtering). Alternatively, by integrating with ESI (Edge Side Includes) technology, dynamic and static content can be separated, caching only the static portions.

How can I monitor the operational status of Varnish Cache?
Built-in varnishstat、Varnishtop Command-line tools enable real-time monitoring of metrics such as cache hit rate, traffic volume, and request latency. They also support integration with third-party monitoring systems like Prometheus and Grafana via APIs, enabling visual monitoring and alerts.

What is the difference between Varnish Cache and Nginx caching?
Varnish specializes in caching acceleration, offering superior in-memory caching performance and more flexible caching strategies; Nginx focuses more on web services and reverse proxy, with relatively basic caching capabilities. In high-traffic caching scenarios, Varnish typically performs better, while Nginx is suitable for lightweight caching or integrated deployment requirements.

What are the core differences between the commercial version and the community version?
The commercial edition (Varnish Enterprise) adds advanced caching features, security protections (such as DDoS defense), cluster management tools, 24/7 technical support, and SLA guarantees, making it suitable for enterprise-level production environments. The community edition is ideal for small-to-medium scale scenarios or technical validation.

Does Varnish Cache support the HTTPS protocol?
Community Edition requires coordination Varnish Modules Extend or integrate with TLS termination tools like Nginx or HAProxy to enable HTTPS support; the commercial edition includes native TLS termination capabilities, allowing direct handling of HTTPS requests.

Editor's Note

Varnish Cache leverages its core strengths of “high performance and high flexibility” to serve as the preferred open-source solution for accelerating static resources and optimizing dynamic content in high-traffic scenarios. The Community Edition is ideal for small and medium-sized enterprises or developers with operational capabilities, delivering robust caching functionality at no cost. The Commercial Edition, meanwhile, meets the stability and security demands of enterprise-level production environments through comprehensive support and advanced features.

It is important to note that Varnish Cache relies primarily on the VCL language for configuration, which imposes a certain technical threshold on operations personnel. For first-time users, it is recommended to consult the official documentation or opt for commercial support services to ensure optimal configuration and stable operation. For scenarios requiring rapid deployment and low technical barriers, consider comparing commercial CDN services or other out-of-the-box caching solutions.