With increasing website traffic and users' increasing demands for page load speed, optimizing website responsiveness has become a top priority for every webmaster. This is especially true for websites hosted on US VPSs, where loading speed can be a significant challenge due to VPS resource limitations and physical distance. To improve website access speed and stability, CDN and caching are essential technologies. This article details how to use CDN and caching to accelerate websites hosted on US VPSs, providing configuration guidelines and FAQs.

　　Ⅰ. How CDNs Accelerate Websites

　　CDNs deploy multiple cache servers globally to cache a website's static resources (such as images, CSS, and JavaScript files) on servers closer to users, thereby improving website loading speed and availability. By using a CDN, user requests are automatically routed to the server closest to them, reducing latency and packet loss caused by distance and significantly improving website responsiveness.

　　CDNs accelerate website access through the following steps:

　　Content Caching: A CDN caches a website's static content on node servers around the world. Every time a user requests a website, the CDN forwards the request to the server closest to the user and provides the cached content.

　　Intelligent Routing: The CDN uses intelligent routing technology to select the optimal server. By analyzing the current network status and server load, it dynamically chooses the most appropriate server to respond.

　　Load Balancing: The CDN's node servers can share the load of the origin server, preventing a single server from crashing or responding slowly due to excessive traffic.

　　II. Cache Configuration Guide

　　Caching is a technique for temporarily storing data between the data source and the end user. Its purpose is to reduce repeated data access, improve response speed, and improve system performance. In website acceleration, the primary goal of caching is to store frequently used dynamic data, database query results, etc., in memory or disk, thereby reducing the processing time of each request.

　　Web Server Cache Configuration

　　1. Nginx Cache Configuration

　　As a high-performance web server, Nginx is often used for reverse proxy and load balancing. Nginx's cache configuration is very flexible and can be configured in the following ways:

　　Configuring Static File Caching:

　　In the Nginx configuration file, use the location block to set cache rules. For example, to cache all image files, you can use the following configuration:

location ~* \.(jpg|jpeg|png|gif|css|js)$ {
    expires 30d;
    add_header Cache-Control "public";
}

　　This configuration will cache images, CSS, and JavaScript files for 30 days. The expires directive sets the expiration time, and Cache-Control specifies the caching policy.

　　Configuring Reverse Proxy Caching:

　　Nginx can also be used as a reverse proxy to cache dynamic content. To configure reverse proxy caching, you can use the following methods:

proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=cache_zone:10m inactive=60m max_size=100m;
server {
    location / {
        proxy_cache cache_zone;
        proxy_cache_valid 200 1h;
        proxy_cache_use_stale error timeout updating;
        proxy_pass http://backend;
    }
}

　　This configuration stores the reverse proxy cache in the /var/cache/nginx directory and caches responses with a 200 status code for one hour.

　　2. Apache Cache Configuration

　　For Apache servers, caching can be implemented using the mod_cache module. The following is a simple cache configuration example:

<IfModule mod_cache.c>
    CacheEnable disk /
    CacheRoot /var/cache/apache2
    CacheDefaultExpire 3600
    CacheMaxExpire 86400
</IfModule>

　　This configuration caches all pages, with a default cache time of 1 hour and a maximum cache time of 24 hours.

　　3. Database Cache Configuration

　　Database query speed is often a bottleneck in website performance. Introducing database caching can significantly improve data query efficiency. Common caching systems include:

　　Redis: Redis is a high-performance in-memory data storage system widely used for caching database query results. You can use Redis in your application to cache database query results and reduce repeated database access.

redis-server

　　You can use the Redis client to cache query results in your application:

import redis
r = redis.Redis(host='localhost', port=6379, db=0)
r.set('user:1000', 'John Doe')
user = r.get('user:1000')

　　Memcached: Memcached is a distributed memory object caching system suitable for caching data and reducing database load.

　　Configuring Memcached in your application, similar to Redis, improves database access speed by caching frequently used query results.

　　4. Browser Caching

　　Browser caching refers to caching static resources in the user's browser, thereby reducing the number of page requests required for reloads. You can configure browser caching policies by configuring HTTP headers (such as Cache-Control and Expires). For example:

location /assets/ {
    expires 30d;
    add_header Cache-Control "public, max-age=2592000";
}

　　This configuration caches static assets under the /assets/ path for 30 days.

　　5. Combining Redis with CDN Caching

　　When using CDN acceleration, combining Redis caching can further improve website performance. Redis can store frequently accessed data, reducing CDN cache misses and improving user access speed. Combining Redis and CDN caching strategies can accelerate both dynamic content and static assets.

　　III. FAQs

　　Q1: Does using a CDN to accelerate website traffic increase server load?

　　A: The purpose of a CDN is to reduce server load by caching static content, thereby alleviating pressure on origin servers. Data is only requested from the origin server when the CDN cache misses, so using a CDN generally does not increase server load.

　　Q2: Does a CDN affect the caching of dynamic content?

　　A: A CDN primarily accelerates the loading of static content. For dynamic content, a CDN does not cache and always retrieves the latest data from the origin server. Therefore, a CDN has no effect on the loading of dynamic content, but it does reduce the load on the origin server.

　　Q3: How can I ensure that cached content does not expire too quickly?

　　A: You can ensure that cached content remains valid for a certain period of time by setting appropriate cache expiration times and cache-control headers. You should configure the cache duration appropriately based on the frequency of access to different content.