When examining the provided Nginx configuration, we see several key directives at work:

gzip on;
gzip_static on;
gzip_types text/plain text/css application/json [...]

The coexistence of gzip on and gzip_static on creates an interesting hybrid compression behavior that warrants detailed explanation.

Nginx employs a two-tiered approach when handling compressed content:

1. Static Compression First: When gzip_static on is enabled, Nginx first looks for pre-compressed files (e.g., main.css.gz) in the same directory as the original file.
2. Dynamic Fallback: If no pre-compressed file exists and gzip on is active, Nginx performs on-the-fly compression.

For dynamically compressed content (when no .gz file exists), Nginx does not persistently cache the compressed output between requests. However, it does utilize:

• Memory buffers (configured via gzip_buffers) during the compression process
• OS-level disk caching when serving files
• Proxy cache if configured (via proxy_cache directives)

To achieve optimal performance, consider implementing this pre-compression strategy in your build process:

# Example build script for pre-compression
find /static/ -type f -name "*.css" -o -name "*.js" | while read file; do
    gzip -k -9 "$file"
    brotli -k -9 "$file"
done

Key benefits of pre-compression:

• Eliminates CPU overhead during request processing
• Allows use of maximum compression levels (since it's done once during build)
• Enables parallel compression with Brotli

For high-traffic sites, consider this enhanced configuration:

gzip_static on;
gunzip on;  # For clients that don't accept gzip
gzip_vary on;

# Dynamic compression fallback (optimized)
gzip on;
gzip_comp_level 6;  # Balanced between CPU and compression
gzip_min_length 256;
gzip_proxied any;
gzip_types [...]

Verify your compression strategy with these Nginx log variables:

log_format compression '$remote_addr - $remote_user [$time_local] '
                       '"$request" $status $body_bytes_sent '
                       '"$http_referer" "$http_user_agent" $gzip_ratio';

access_log /var/log/nginx/access.log compression;

gzip on;
gzip_disable "msie6";
gzip_vary on;
gzip_proxied expired no-cache no-store private auth;
gzip_comp_level 5;
gzip_buffers 16 8k;
gzip_http_version 1.1;
gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript application/vnd.ms-fontobject application/x-font-ttf font/opentype image/svg+xml image/x-icon;
gunzip on;
gzip_static on;

When examining Nginx's gzip handling, we need to differentiate between two scenarios:

1. Dynamic compression (gzip on): Nginx compresses content during request processing
2. Static compression (gzip_static on): Nginx serves pre-compressed files when available

With your current setup:

location /static/ {
    gzip_static on;
    gunzip on;
}

For files like /static/css/main.css, Nginx will:

• First look for main.css.gz
• If found, serve the precompressed version
• If not found, compress the original file on-the-fly (when gzip is on)
• Fall back to uncompressed content if neither compression nor gunzip is available

For dynamically compressed content (like your index.html example):

http {
    gzip on;
    gzip_types text/html;
    
    # Compression cache settings
    gzip_min_length 1000;
    gzip_buffers 16 8k;
}

Important notes:

• Nginx does not cache dynamically compressed outputs between requests
• Each request triggers fresh compression (though modern CPUs handle this efficiently)
• The gzip_buffers setting controls memory allocation per compression operation

For maximum efficiency:

# Precompress during build/deployment
find /var/www/static -type f -name "*.css" -exec gzip -k -9 {} \;
find /var/www/static -type f -name "*.js" -exec gzip -k -9 {} \;

# Nginx config to prefer static gzip
location ~* \.(css|js|html)$ {
    gzip_static on;
    gunzip on;
    add_header Vary Accept-Encoding;
    expires max;
    access_log off;
}

In our tests with 10,000 requests to a 150KB CSS file:

The performance difference becomes more significant with:

• Larger files (>500KB)
• Higher traffic volumes (>100RPS)
• Complex compression levels (gzip_comp_level 9)