Varnish Cache Reverse Proxy Speeds Up Server 10 Times: The Secret

I remember one time I received an "emergency" project for an e-commerce website on Black Friday. The page loading speed is sluggish, the server CPU always peaks at 100%, and customers constantly complain about not being able to pay. After a long night of struggling with log files, I found my "true love" named Varnish.

The results after deployment were surprising: website speed skyrocketed nearly 10 times, the server breathed a sigh of relief even though traffic continued to pour in. That's not some distant technological miracle, but the secret of Varnish Cache reverse proxy to speed up the server that I'm about to share with you in detail right in this article.

Why is Varnish Cache a "savior" for your server?

Varnish Cache acts as a super-fast HTTP accelerator, helping to reduce the direct load on the backend server and shorten page load times to milliseconds.

At Pham Hai, we often advise DevOps engineers and system administrators to prioritize considering this solution when the system begins to show signs of overload. Optimizing server infrastructure is not simply about "burning money" to constantly upgrade RAM or CPU. Sometimes, why should you use Varnish Cache is the easiest question to answer when you look at the graph of resource consumption suddenly dropping from 90% to less than 10%. Based on the latest 2026 performance reports, this tool truly makes a transformative difference to any web system.

What is Varnish Cache that is so "divine"?

Varnish Cache is an open source software that acts as a caching HTTP reverse proxy, placed in front of a web server to store copies of web pages.

In simple terms, what is Varnish Cache? It is a specialized HTTP accelerator specifically designed for websites with high traffic and complex dynamic content. Instead of letting the web server (like Apache or Nginx) have to work hard to reprocess the same HTTP requests thousands of times, Varnish will stand tall at the frontend, absorbing all traffic from users. If the data the user needs is already in the cache, it will return immediately without calling the backend.

This plays an extremely important role in the enterprise's content distribution network. If you are learning What is CDN and why websites need to use CDN, you will realize that Varnish's mechanism is similar to an internal CDN node (Edge Cache) located right at your origin server. It helps you be completely proactive about data and response speed.

The undeniable benefits of using Varnish Cache

Varnish Cache provides outstanding benefits in terms of page load speed, flexible system scalability, and significant server resource savings.

The benefits of Varnish Cache are most clearly demonstrated through three core aspects that every IT project aspires to achieve:

• Thời gian tải trang siêu tốc: Varnish Cache tăng tốc website lên từ 300 đến 1000 lần so với thông thường. Dữ liệu được phục vụ trực tiếp từ RAM, bỏ qua hoàn toàn độ trễ của ổ cứng (dù là NVMe) hay các truy vấn database nặng nề.
• Giảm tải máy chủ cực mạnh: Backend server không phải render lại các trang tĩnh hay thực thi mã PHP liên tục. Điều này góp phần nâng cao tuổi thọ phần cứng và giảm chi phí duy trì cloud server.
• Khả năng mở rộng: Hệ thống dễ dàng chịu được các đợt traffic spikes (đột biến truy cập) mà không bị sập, cải thiện tối đa trải nghiệm người dùng trong các dịp chạy chiến dịch marketing lớn.

Another great Varnish branded feature is Grace Mode. This feature allows the system to continue serving old content (stale content) to visitors in case the backend server temporarily fails or restarts. Thanks to that, your website is always "alive" and professional in the eyes of users.

Mechanism of action: Decoding Cache HIT and Cache MISS

Varnish Cache works based on checking requests from users; If valid data is available, it will be returned immediately (Cache HIT), otherwise it will be requested from the backend (Cache MISS).

Many newcomers often wonder how Varnish Cache works in a real environment. When an HTTP request is sent to the system, Varnish will act as the first stop and execute the following logic flow:

• Cache HIT: Varnish tìm thấy bản sao hợp lệ của trang web trong bộ nhớ đệm. Nó lập tức trả về cho trình duyệt của người dùng chỉ trong vài micro-giây. Backend server thậm chí không hề biết đến sự tồn tại của request này.
• Cache MISS: Dữ liệu chưa có trong cache hoặc đã hết hạn (TTL - Time to Live). Lúc này, Varnish mới chuyển tiếp request đến backend server, chờ nhận phản hồi, lưu một bản sao vào cache rồi mới gửi cho người dùng.

To optimize web performance with Varnish Cache to the highest level, system architects often combine it with other caching solutions at a lower level. For example, use Varnish for the frontend and integrate Redis cache to accelerate web applications for the database backend. This combination of web stream caching and object caching creates a perfect architecture, despite any traffic limitations.

Let's get started: Detailed instructions for installing and configuring Varnish Cache

The deployment process includes installing the software package, changing the port of the current web server and configuring Varnish to listen on standard port 80.

At Pham Hai, we always emphasize practicality and immediate applicability. Below is a detailed way to install Varnish Cache, based on the latest operating system updates as of 2026. Make sure you have root or sudo rights on the server before typing the first commands.

Step 1: Install Varnish Cache on Ubuntu and CentOS

You can easily install Varnish through the apt package manager on Ubuntu operating system or dnf/yum on CentOS environment.

Việc triển khai Varnish Cache trên Ubuntu (áp dụng cho các bản LTS như 22.04 hoặc 24.04) diễn ra rất mượt mà. Bạn chỉ cần mở terminal và chạy cụm lệnh sau để lấy gói mới nhất: sudo apt update && sudo apt install varnish -y

Đối với môi trường Varnish Cache trên CentOS / RHEL / AlmaLinux, bạn cần bật kho lưu trữ EPEL trước khi tiến hành cài đặt: sudo dnf install epel-release -y && sudo dnf install varnish -y

Sau khi quá trình cài đặt hoàn tất, bạn cần thiết lập để dịch vụ tự động chạy mỗi khi reboot máy chủ bằng lệnh sudo systemctl enable varnish. Lưu ý rằng theo mặc định của nhà phát triển, Varnish sẽ lắng nghe trên port 6081. Chúng ta sẽ cần tinh chỉnh lại để nó chạy trên port 80 (HTTP) ở các bước tiếp theo để trực tiếp đón người dùng.

Step 2: Configure Varnish as a reverse proxy for Nginx/Apache

You must switch Nginx/Apache to listen on a hidden port (eg 8080) and set up Varnish to run on port 80 to directly receive traffic from the internet.

To configure Varnish Cache Nginx or configure Apache, the vital first step is to open the web server's configuration file and change the default port from 80 to another port, usually 8080. If you are building a new system from scratch and wondering between these two web server platforms, the article Nginx vs Apache web server comparison 2026 will provide a detailed perspective to help you make the most accurate architectural decision.

Tiếp theo, bạn mở file cấu hình chính của Varnish tại /etc/varnish/default.vcl và chỉ định backend server trỏ về port 8080 mà bạn vừa đổi:

backend default {
    .host = "127.0.0.1";
    .port = "8080";
}

Cuối cùng, cập nhật tham số khởi động của Varnish bằng lệnh sudo systemctl edit varnish. Sửa cờ -a :6081 thành -a :80 và cấp phát RAM cho cache (ví dụ: -s malloc,1G). Khởi động lại dịch vụ bằng systemctl daemon-reload và systemctl restart varnish. Chúc mừng, Varnish đã chính thức làm reverse proxy đứng chắn bảo vệ web server của bạn.

Step 3: Optimize for the "national website" WordPress

Configuring Varnish for WordPress requires excluding admin pages (wp-admin) and login cookies to avoid mistakenly caching dynamic user data.

Instructions for configuring Varnish Cache for WordPress is always a rather specific topic. Because WordPress uses a lot of cookies and PHP sessions to manage user state, if you configure VCL poorly, you can accidentally cache the admin page (wp-admin) or WooCommerce cart of one customer for another customer to see, causing a security disaster.

Để giải quyết triệt để, bạn cần thêm các quy tắc bỏ qua cache vào file default.vcl đối với các request có chứa cookie wordpress_logged_in hoặc URL chứa /wp-admin. Việc thiết lập chuẩn chỉ này sẽ giúp tăng tốc độ website wordpress một cách an toàn và bền vững. Đồng thời, yếu tố hạ tầng cũng cực kỳ quan trọng; bạn nên ưu tiên chọn một VPS giá rẻ tốt nhất cho WordPress 2026 có tốc độ đọc ghi đĩa cứng (NVMe) cao để hệ thống hoạt động mượt mà nhất.

Besides, if your project is using LiteSpeed ​​Web Server instead of traditional Nginx/Apache, you can refer to configuring litespeed cache wordpress because this platform has its own cache (LSCache) deeply integrated into the server core which is very powerful. However, in large and complex microservices architecture systems, Varnish still holds the throne.

Varnish Cache in real combat: Comparison and difficult questions

In a real-world environment, engineers need to consider between Varnish and Nginx Cache, as well as solve the SSL/TLS problem and tweak the VCL language in depth.

When bringing a system from a test environment to Production, theory alone is not enough. Below are the core architectural issues that our Pham Hai team often has to handle and optimize for large corporate partners.

Varnish Cache vs. Nginx Cache: Who to choose, who to leave?

Varnish excels in pure in-memory flexibility and speed, while Nginx Cache is easier to configure because it is built into the web server.

Comparing Varnish Cache and Nginx Cache is always a hotly debated topic, consuming a lot of ink on technology forums. Nginx FastCGI Cache or Proxy Cache works very well, but it is still essentially a "bonus" feature of a general-purpose web server. On the contrary, Varnish Cache is a software created with only one mission: to make professional web caching.

According to the latest performance tests (benchmarks) in 2026, Varnish handles a slightly higher number of concurrent requests thanks to its separate Threading and memory management mechanisms. However, Nginx is friendlier and easier to set up for newbies. If your KPI is simply optimize ttfb for wordpress on vps, both will complete the task excellently. But if you need to customize complex cache logic based on HTTP headers, mobile devices or geolocation, Varnish is the absolute winner.

Does Varnish Cache "play" with SSL/TLS?

The open source version of Varnish Cache does not support SSL/TLS directly, you need to use another proxy like Nginx or Hitch in front of it to decrypt.

A classic question from sysadmins: Does Varnish Cache support SSL? The short answer is No (for the free open source version). The Varnish development team has a very clear design philosophy: SSL/TLS encryption and decryption consumes a lot of CPU cycles. They wanted to let specialized tools handle this to keep Varnish as light, focused, and fast as possible.

The industry standard solution is to use the SSL Termination architecture. You will place Nginx (or Hitch TLS proxy) on port 443 to receive and decrypt HTTPS connections from users, then push plain HTTP traffic (port 80 or 8443) behind for Varnish to process. You can see more instructions Nginx configure SSL reverse proxy to set up this security load balancing model correctly, avoiding annoying redirect loop errors.

What is VCL? The "secret weapon" that makes the difference

VCL (Varnish Configuration Language) is Varnish's own configuration language, allowing detailed programming of how the cache handles each request.

What is VCL in Varnish Cache? VCL (Varnish Configuration Language) is the soul, the "secret weapon" that creates the gap between Varnish and the rest of the caching world. Unlike regular static text config files (like Nginx or Apache's .conf files), VCL is essentially a domain-specific programming language (Domain-Specific Language).

When Varnish starts, all of your VCL code will be compiled directly into C code by the system, then loaded directly into memory to run. This allows you to write extremely complex rules: from load balancing between dozens of backend servers, to changing HTTP headers on-the-fly, to cleaning up tracking cookies (like Google Analytics) to increase Cache HIT rates. All of this logic is executed at the speed of pure C.

Don't let slow page load speeds be a barrier to business growth. Using Varnish Cache reverse proxy to speed up your server is not just a temporary technical trick, it is actually a strategic investment in your system architecture. Whether you are managing a small personal blog or a large-scale e-commerce system with millions of pageviews, taking the time to learn and implement Varnish will definitely bring sweet results in terms of performance and stability. Proactively turn website speed into your strongest competitive advantage in the digital market.

Have you ever implemented Varnish Cache for your project yourself? Please share your practical experiences, favorite VCL code snippets or any difficulties you are encountering in the comments section below, we will discuss and troubleshoot together!

Note: The information in this article is for reference only. For the best advice, please contact us directly for specific advice based on your actual needs.