Configure CDN Rules

Why CDN configuration matters

Default CDN settings work for most sites, but they are a compromise. Your marketing landing pages might benefit from aggressive caching, while your checkout flow needs no caching at all. Custom CDN rules let you fine-tune performance for each part of your site without sacrificing content freshness.

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Set cache headers in your application

The CDN respects HTTP cache headers sent by your application. The most direct way to control caching is to set these headers in your code.

ASP.NET Core response caching

Add the response caching middleware and set cache profiles:

builder.Services.AddResponseCaching();

// In your middleware pipeline
app.UseResponseCaching();

Apply cache profiles to controllers or pages:

[ResponseCache(Duration = 600, VaryByHeader = "Accept-Language")]
public IActionResult Index()
{
    return View();
}

Per-route cache rules

For different cache behavior on different URL patterns, use middleware:

app.Use(async (context, next) =>
{
    var path = context.Request.Path.Value;

    if (path.StartsWith("/api/"))
    {
        context.Response.Headers["Cache-Control"] = "no-store";
    }
    else if (path.StartsWith("/static/"))
    {
        context.Response.Headers["Cache-Control"] = "public, max-age=31536000, immutable";
    }

    await next();
});

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Configure CMS output cache

Optimizely CMS has a built-in output cache that works with the CDN layer. Configure it in your startup:

services.Configure<OutputCacheOptions>(options =>
{
    options.DefaultExpiration = TimeSpan.FromMinutes(10);
});

Cache by content type

Set different cache durations for different content types:

services.AddOutputCache(options =>
{
    options.AddPolicy("LongCache", builder =>
        builder.Expire(TimeSpan.FromHours(1)));
    options.AddPolicy("ShortCache", builder =>
        builder.Expire(TimeSpan.FromMinutes(2)));
});

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Set custom response headers

Add custom headers for security, CORS, or debugging through middleware:

app.Use(async (context, next) =>
{
    context.Response.Headers["X-Content-Type-Options"] = "nosniff";
    context.Response.Headers["X-Frame-Options"] = "SAMEORIGIN";
    context.Response.Headers["Strict-Transport-Security"] = "max-age=31536000; includeSubDomains";

    await next();
});

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Purge the CDN cache

Automatic purge on publish

When editors publish content, the CMS automatically purges affected URLs from the CDN. This is handled by the built-in cache invalidation system. No additional configuration is needed for this default behavior.

Manual purge via portal

1. Log into the management portal
2. Navigate to your project
3. Go to CDN > Purge Cache
4. Choose purge scope:
   • Single URL — Enter the exact URL to purge
   • Path prefix — Enter a path like /en/blog/ to purge all matching URLs
   • Full purge — Clear the entire CDN cache
5. Click Purge

Purge via CLI

opti cdn purge --url "https://www.example.com/en/blog/" --environment Production
opti cdn purge --all --environment Integration

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Cache debugging

Verify cache status

Check the response headers to confirm caching behavior:

curl -I https://www.example.com/en/

Look for these headers:

Header	Meaning
X-Cache: HIT	Response served from CDN cache
X-Cache: MISS	Response fetched from origin
Age: 120	Content has been cached for 120 seconds
Cache-Control: public, max-age=600	Cacheable for 10 minutes

Common issues

Symptom	Cause	Fix
Pages never cache	Cache-Control: private or no-store	Check middleware and CMS output cache settings
Stale content after publish	Purge not triggering	Verify CMS event handling; manual purge as fallback
Different content per user	Vary: Cookie creating too many variants	Reduce cookie variation; use client-side personalization
Static assets not caching	Missing cache headers on static files	Enable static file caching middleware

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Recommended cache strategy

URL pattern	Cache-Control	Rationale
/static/*, /assets/*	public, max-age=31536000, immutable	Versioned files; cache forever
/en/* (CMS pages)	public, max-age=600	Content pages; 10-minute cache
/api/*	no-store	Dynamic API responses
/episerver/*	no-store	CMS editor interface
/util/*	no-store	Utility and health endpoints

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Related resources

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