Configuring the Nginx Server Block with FastCGI Cache

FastCGI cache is powerful, but it is only one layer of WordPress speed work. I explain the full stack in my WordPress performance stack guide.

This is the most important config file in the entire stack. Everything before this — Nginx installation, MariaDB, PHP-FPM — was preparation. This server block is what tells Nginx how to actually serve your WordPress site.

The config below is what I run on my own server. Every directive is explained so you know what you’re putting on your machine, not just that it works.

Server-Level Cache vs Plugin Cache — Before You Start

If you’re coming from shared hosting, you probably know WordPress caching through plugins: W3 Total Cache, WP Super Cache, WP Rocket. These work by generating static HTML files inside WordPress’s directory and serving them instead of re-running PHP each time.

FastCGI cache is fundamentally different — and understanding the difference matters before you configure it.

Without cache:
Browser → Nginx → PHP-FPM → WordPress → MariaDB → HTML → Browser
                  (PHP runs every time)

With plugin cache (WP Rocket etc.):
Browser → Nginx → PHP-FPM → WordPress checks cache → serves HTML file
                  (PHP still runs, but less work)

With FastCGI cache (HIT):
Browser → Nginx → serves cached HTML directly
                  (PHP never runs)

FastCGI cache operates at the Nginx layer — before PHP is even involved. A cache hit means zero PHP execution, zero database queries. The performance difference on real traffic is significant.

The WP Rocket disk space problem on VPS:

WP Rocket’s page cache creates a static HTML copy of every page on your site — stored in /wp-content/cache/. On a site with hundreds of posts, this can grow to several gigabytes. On shared hosting where disk space is managed for you, this goes unnoticed. On a VPS where you’re watching df -h yourself, it shows up fast.

If you’re running WP Rocket on a VPS and wondering why disk usage keeps climbing, check:

du -sh /var/www/yoursite/wp-content/cache/

With FastCGI cache enabled at the Nginx level, WP Rocket’s page cache is redundant. This config disables it. WP Rocket’s other features (minification, lazy loading, database cleanup) still run — just not page caching.

Step 1 — Create the Cache Directory

FastCGI cache needs a directory to store cached pages:

sudo mkdir -p /var/cache/nginx/fastcgi
sudo chown nginx:nginx /var/cache/nginx/fastcgi

Step 2 — Add FastCGI Cache Config to nginx.conf

Open the main Nginx config:

sudo nano /etc/nginx/nginx.conf

Inside the http {} block, add these lines before the include /etc/nginx/conf.d/*.conf; line:

# FastCGI cache zone definition
fastcgi_cache_path /var/cache/nginx/fastcgi
    levels=1:2
    keys_zone=WORDPRESS:100m
    inactive=60m
    max_size=1g;

fastcgi_cache_key "$scheme$request_method$host$request_uri";

What this does:

• fastcgi_cache_path — where cached files are stored on disk
• levels=1:2 — directory structure for cache files (prevents thousands of files in one folder)
• keys_zone=WORDPRESS:100m — name the cache zone and allocate 100MB of RAM for the index
• inactive=60m — remove cached items not accessed for 60 minutes
• max_size=1g — maximum disk space for the cache
• fastcgi_cache_key — how Nginx identifies unique pages (scheme + method + domain + URL)

Save and exit.

Step 3 — Create the WordPress Server Block

Create a new config file for your domain:

sudo nano /etc/nginx/conf.d/yourdomain.conf

Paste the complete config below, replacing yourdomain.com with your actual domain and /var/www/yourdomain.com with your actual web root path:

# Cache bypass conditions
# These variables determine when NOT to serve cached content
map $http_cookie $no_cache_cookies {
    default         0;
    ~SESS            1;  # PHP sessions
    ~wordpress_logged_in 1;  # Logged in users
    ~comment_author  1;  # Comment authors
    ~woocommerce_    1;  # WooCommerce (cart, checkout)
}

server {
    listen 80;
    listen [::]:80;
    server_name yourdomain.com www.yourdomain.com;

    # Redirect HTTP to HTTPS (after SSL is installed in Part 5)
    # Uncomment after running Certbot:
    # return 301 https://$host$request_uri;

    root /var/www/yourdomain.com;
    index index.php index.html;

    # Access and error logs
    access_log /var/log/nginx/yourdomain.com.access.log;
    error_log  /var/log/nginx/yourdomain.com.error.log;

    # Security headers
    add_header X-Frame-Options "SAMEORIGIN" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header X-XSS-Protection "1; mode=block" always;

    # Hide Nginx version
    server_tokens off;

    # Gzip compression
    gzip on;
    gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript;
    gzip_min_length 1000;

    # FastCGI cache settings for this server
    set $skip_cache 0;

    # Don't cache POST requests
    if ($request_method = POST) {
        set $skip_cache 1;
    }

    # Don't cache URLs with query strings
    if ($query_string != "") {
        set $skip_cache 1;
    }

    # Don't cache WordPress admin, login, or special pages
    if ($request_uri ~* "(/wp-admin/|/xmlrpc.php|/wp-login.php|wp-.*.php|index.php|/feed/|sitemap(_index)?.xml)") {
        set $skip_cache 1;
    }

    # Don't cache if user has special cookies (logged in, WooCommerce active)
    if ($no_cache_cookies = 1) {
        set $skip_cache 1;
    }

    # Main location block — WordPress permalink handling
    location / {
        try_files $uri $uri/ /index.php?$args;
    }

    # PHP-FPM processing
    location ~ \.php$ {
        # Security: block access to PHP files in uploads
        try_files $uri =404;
        fastcgi_split_path_info ^(.+\.php)(/.+)$;

        # Connect to PHP-FPM via Unix socket
        fastcgi_pass unix:/run/php-fpm/www.sock;
        fastcgi_index index.php;

        # Standard FastCGI params
        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_param PATH_INFO $fastcgi_path_info;

        # FastCGI cache directives
        fastcgi_cache WORDPRESS;
        fastcgi_cache_valid 200 301 302 1h;  # Cache successful responses for 1 hour
        fastcgi_cache_bypass $skip_cache;
        fastcgi_no_cache $skip_cache;

        # Add cache status header (for debugging — shows HIT/MISS/BYPASS)
        add_header X-Cache-Status $upstream_cache_status always;

        # Timeouts
        fastcgi_read_timeout 300;
        fastcgi_buffers 16 16k;
        fastcgi_buffer_size 32k;
    }

    # Static files — served directly, no PHP needed
    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
        expires max;
        log_not_found off;
        access_log off;
    }

    # Deny access to sensitive files
    location ~ /\. {
        deny all;
        access_log off;
        log_not_found off;
    }

    location = /favicon.ico {
        log_not_found off;
        access_log off;
    }

    location = /robots.txt {
        allow all;
        log_not_found off;
        access_log off;
    }

    # Block access to WordPress config and sensitive files
    location ~* wp-config.php {
        deny all;
    }
}

Understanding the Key Directives

try_files $uri $uri/ /index.php?$args This handles WordPress pretty permalinks. When someone visits /about/, Nginx checks if a file called about exists, then if a directory called about/ exists, and if neither, passes the request to WordPress’s index.php. Without this, only the homepage works.

fastcgi_pass unix:/run/php-fpm/www.sock Sends PHP requests to the Unix socket we configured in the previous article. Must match the listen value in /etc/php-fpm.d/www.conf.

fastcgi_cache WORDPRESS Enables caching using the zone defined in nginx.conf. WORDPRESS is the zone name — it must match keys_zone=WORDPRESS:100m exactly.

fastcgi_cache_bypass $skip_cache and fastcgi_no_cache $skip_cache Two separate directives that both need to be set. bypass tells Nginx not to serve a cached response. no_cache tells Nginx not to store the response in cache. Both are needed to fully disable caching for the conditions we defined.

add_header X-Cache-Status $upstream_cache_status always Adds a header to responses showing whether the page was served from cache (HIT), generated fresh (MISS), or deliberately bypassed (BYPASS). Used for debugging — check it with curl -I https://yourdomain.com.

The $skip_cache bypass rules Four conditions that bypass the cache:

1. POST requests — form submissions must reach PHP
2. URLs with query strings — search results, paginated content
3. WordPress admin paths — dynamic, user-specific
4. Cookie-based bypass — logged-in users, WooCommerce sessions

Step 4 — Test and Apply

# Test for syntax errors
sudo nginx -t

# If test passes, reload
sudo systemctl reload nginx

If nginx -t shows an error, it will point to the file and line number. Common issues:

• Missing semicolon at end of a directive
• Typo in the domain name
• Wrong PHP-FPM socket path

Basic Server Block Variants

Redirect all HTTP to HTTPS (use after SSL setup in Part 5):

server {
    listen 80;
    server_name yourdomain.com www.yourdomain.com;
    return 301 https://$host$request_uri;
}

Redirect www to non-www:

server {
    listen 443 ssl;
    server_name www.yourdomain.com;
    return 301 https://yourdomain.com$request_uri;
}

Block direct IP access (returns 444 — drops connection):

server {
    listen 80 default_server;
    server_name _;
    return 444;
}

Save these in your personal config notes — they come up repeatedly.