Tencent Cloud Bulk Top-up Discounts Tencent Cloud CDN Cache Configuration Best Practices

Introduction: Why CDN Cache Configuration Matters

CDN isn’t just a “speed switch.” Its real value shows up when cache is configured deliberately—so users get faster responses, your origin server is protected from traffic spikes, and your system behaves predictably when content changes. For Tencent Cloud CDN, cache configuration is essentially the art of matching what you serve with how the CDN should store it, when it should refresh, and which requests should bypass caching.

This article outlines practical best practices for Tencent Cloud CDN cache configuration. The focus is on decisions you can make immediately: setting cache-control headers, choosing caching rules, handling dynamic content, managing query strings, planning invalidation, and validating results with real metrics. Even if you already enabled CDN, these practices help you avoid the common pitfalls that lead to low cache hit rates, unnecessary origin pressure, and confusing “why didn’t it update?” moments.

Start With the Cache Model: What the CDN Actually Caches

Before touching any settings, clarify how CDN will treat your responses. In most CDN architectures, caching is determined by a mix of:

• Tencent Cloud Bulk Top-up Discounts Cache headers returned by your origin (for example, Cache-Control, Expires, and sometimes ETag/Last-Modified behavior).
• CDN cache rules you configure (matching paths, domains, request parameters, and query behavior).
• Request characteristics such as query strings, headers, cookies, and user-agent rules.

In practice, the most stable approach is to make the origin tell the truth via headers, then use CDN rules to handle edge cases. If you rely entirely on CDN rules while the origin sends ambiguous or conflicting headers, your results can vary across content types and deployment cycles.

Define Content Categories Up Front

A “best practice” cache strategy starts with categorizing content. A simple and effective approach:

• Static immutable assets: JS/CSS bundles with content hashes, images that never change at the same URL, fonts. These should have long TTL.
• Static versioned assets: assets that may update when the version changes (e.g., /v2/app.js). TTL can be moderate to long.
• Semi-dynamic resources: landing pages’ components, search suggestions with short lifetimes, frequently refreshed feeds.
• Fully dynamic content: user-specific pages, authenticated endpoints, frequently changing dashboards. These usually should not be cached globally.

Once you know what each URL family represents, configuring cache becomes more predictable. You won’t accidentally cache personalized content or invalidate huge portions of CDN because a global rule was too broad.

Use Cache-Control Headers Correctly (Your Most Reliable Lever)

Cache-Control is the language your origin uses to instruct caching behavior. Even with CDN configuration, these headers remain the first line of control.

For Immutable Static Assets: Prefer Long TTL

For hashed filenames (like app.9f3a2c1.js), you can safely cache for a long time because the URL changes when the content changes. Common choices include:

• Cache-Control: public, max-age=31536000, immutable (or a similarly long TTL)
• Ensure you also set an appropriate Content-Type so clients and CDN treat the file correctly.

When you do this, you typically achieve high cache hit rates because the CDN can serve from cache without frequent revalidation.

For Non-Hashed Static Files: Use Shorter TTL or Revalidation

If your URLs stay the same across releases (for example, /css/app.css without a hash), long TTL becomes risky: users may see old content until the cache expires. In this case, choose one of these patterns:

• Short TTL (hours instead of days)
• Revalidation using origin-generated validators (like ETag or Last-Modified) and letting CDN re-check

Tencent Cloud Bulk Top-up Discounts Short TTL reduces stale content but increases origin traffic. Revalidation can balance both, but it depends on your origin’s ability to respond consistently and quickly.

For Dynamic or User-Specific Content: Avoid Caching Unless You Know the Risk

User-specific endpoints should generally send cache headers that prevent shared caching, such as:

• Cache-Control: private, no-store for highly sensitive pages
• Or Cache-Control: no-cache when you want revalidation but not storage

If you accidentally allow caching for authenticated pages, you can create serious correctness and security issues. Even if the CDN respects cookies sometimes, relying on that alone is not a sound strategy.

Design CDN Cache Rules Around URL Patterns

Cache rules in CDN are typically configured by matching paths or patterns. Good rule design is specific, small in scope, and easy to reason about.

Keep Rules Narrow and Order Matters

When you have many rules, it’s easy to create overlaps. A request might match multiple patterns, and the system will apply the highest priority rule. Best practice:

• Start with the most specific patterns (e.g., /static/js/)
• Tencent Cloud Bulk Top-up Discounts Then cover broader ones (e.g., /static/)
• Finally apply a catch-all rule for the rest

This avoids the “shadowing” problem where a broad rule unexpectedly overrides a precise one.

Use Separate TTLs per Content Type

A practical baseline TTL plan:

• Hashed assets: 30–365 days
• Versioned assets: 7–30 days
• Images that can change occasionally: 1–7 days
• HTML pages: often 0–300 seconds depending on your needs
• API responses: generally short or no caching, unless the API is explicitly designed for caching

Don’t treat every file the same. A one-size-fits-all TTL usually produces either stale content complaints or unnecessary origin load.

Handle Query Strings and Cache Keys With Care

Query strings are a frequent source of cache fragmentation. If every unique query creates a unique cache entry, your hit rate can collapse—even if the underlying resource is effectively the same.

Decide Which Query Parameters Actually Affect Content

For example:

• If a query parameter only controls tracking (like utm_source), it should usually be ignored for caching.
• Tencent Cloud Bulk Top-up Discounts If a query parameter changes the returned content (like ?lang=, ?size=, ?filter=), it may need to be part of the cache key—or you need separate endpoints.

Best practice is to explicitly control the cache key logic. Treat query-string behavior as a deliberate design choice, not an accident.

Prefer URL-based Variants Over Query-Based Variants for High Caching Efficiency

Where possible, move content variants into the path:

• Instead of /image?size=300, use /image/size/300

This often results in cleaner cache keys, simpler invalidation, and easier debugging.

Manage Cookies, Authorization, and Headers

CDNs can sometimes vary cache behavior based on cookies or headers. That can be useful, but it can also explode your cache space and reduce hit rates.

Avoid Caching Based on Unstable Cookies

Many applications set cookies for consent, session, or analytics. If the CDN cache key includes those cookies (directly or indirectly), the same asset can be cached multiple times per user segment.

Best practice is to ensure that shared static assets are served without user-specific cookie variation, and that dynamic content is handled with appropriate bypass rules.

For Authenticated APIs: Either Bypass or Use Explicit Caching Strategy

Tencent Cloud Bulk Top-up Discounts There are two safe approaches for authenticated endpoints:

• Tencent Cloud Bulk Top-up Discounts Bypass caching entirely for user-specific responses.
• Implement a proper shared caching layer where the cache key is constructed from an authorization scope that is safe (and not tied to user identity).

Do not “hope” that the CDN will handle authorization safely. Make the rule explicit.

Plan Cache Invalidation and Refresh Strategy

Even with a perfect TTL policy, you need a response plan for content changes. Cache invalidation is where many teams lose control.

Prefer Versioned Asset URLs to Reduce Invalidation Pressure

If you can update assets by changing filenames (hashes or version directories), you avoid the need for frequent invalidation. This is the cleanest strategy because old URLs naturally expire while new ones appear immediately.

Use Invalidation for HTML and Non-Versioned Content—But Scope It

For HTML pages or non-versioned resources, invalidation is sometimes necessary. Best practice:

• Invalidate the smallest set of paths required
• Avoid broad “flush everything” actions
• Schedule invalidation after deploying the new content to the origin to prevent CDN from immediately pulling stale or missing content

Also, clarify with your team what triggers invalidation: a deploy? a release flag? a content publishing event? Make it repeatable.

Understand Propagation Timing and User Experience

Invalidation is not instantaneous in the real world. There is often a propagation window and potential overlap between old and new caches. Your user experience should reflect that reality—such as using cache-busting for critical assets referenced by HTML.

Validate With Metrics: Cache Hit Rate, Origin Load, and Error Patterns

A configuration is only “best” if it works in your environment. Validation turns guesswork into evidence.

Track Cache Hit Rate by Content Type

Monitor hit rate differences across:

• Static assets (JS/CSS/images)
• Tencent Cloud Bulk Top-up Discounts HTML
• APIs or other semi-dynamic endpoints

If static assets have low hit rate, check cache headers, query key settings, and rule matching. If HTML has unusually high hit rate, you might be caching content that should refresh more frequently.

Watch Origin Traffic and Latency Spikes

When CDN works well, origin latency and bandwidth decrease. If you see origin traffic spikes after changing cache rules, it likely means the CDN is no longer caching (or cache TTL is too short). Correlate rule changes with traffic timelines.

Look for Correctness Signals: Stale Content Complaints and Update Delays

Cache issues often show up in the form of user reports: “the page didn’t update,” “I still see yesterday’s logo,” or “CSS looks old.” When complaints rise right after a release, it usually points to either:

• TTL too long for non-versioned resources
• Invalidation scope too wide or mistimed
• Query-string behavior causing unexpected cache misses or hits

Use targeted adjustments rather than random changes.

Common Pitfalls and How to Avoid Them

Pitfall 1: Caching Everything Because It Sounds Fast

Many teams enable caching globally for convenience. But HTML and authenticated pages often should not be cached. The result can be stale UX, session leaks, or inconsistent behavior. Fix by separating static assets from dynamic endpoints and setting explicit cache policies for each group.

Pitfall 2: Long TTL Without Versioned URLs

If you set a long TTL for files whose URL doesn’t change when content changes, stale content is inevitable. Fix by adopting hashed filenames or using safer shorter TTL/revalidation.

Pitfall 3: Query Strings Break Cache Efficiency

When tracking or random query parameters are included in cache keys, you multiply cache variants and reduce hit rate. Fix by ignoring non-content queries or rewriting URLs to include variants in the path.

Pitfall 4: Conflicting Origin Headers and CDN Rules

Tencent Cloud Bulk Top-up Discounts One rule says “cache for 7 days,” but the origin headers say “no-cache.” The system then behaves based on precedence rules and may not cache as you expect. Fix by standardizing a single source of truth: typically origin headers for content types, reinforced by CDN rules for matching logic.

Pitfall 5: No Testing Before Rolling Out

CDN cache changes can be subtle. You might not notice broken behavior until peak traffic. Fix by testing with:

• Real URLs from each content category
• Edge-case query strings
• Authenticated vs unauthenticated flows

Then validate logs and metrics after rollout.

A Practical Baseline Configuration You Can Adapt

The following “starter plan” is a useful baseline. You’ll tailor TTLs and match patterns to your app, but the structure is what matters.

1) Static Hashed Assets

• Match paths like /assets/, /static/, and file extensions such as .js, .css, .png, .jpg, .woff2
• Set origin headers to: public, max-age=31536000, immutable
• In CDN rules, ensure cache key doesn’t vary unexpectedly

2) HTML Pages

• Match paths like / and /pages/ or your SPA entry
• Use short TTL (often 0–60 seconds for highly dynamic sites, longer for calmer traffic)
• Rely on invalidation when you deploy new HTML

3) Images and Media

• Tencent Cloud Bulk Top-up Discounts If images are versioned, allow longer TTL
• If images can change without URL updates, keep TTL short or use revalidation

4) APIs

• Default to bypass unless your API is explicitly designed to be cacheable
• If caching is allowed, restrict it to safe, shared responses and define TTL based on business freshness requirements

Operational Tips for Ongoing Maintenance

Cache configuration isn’t a one-time task. Your product evolves, and so does your content strategy. A few operational habits keep CDN behavior predictable.

Create a Cache Policy Matrix

Maintain a simple internal table:

• URL pattern
• Content type
• Expected TTL
• Whether query strings are part of cache key
• Invalidation rules (if any)

This makes future changes safer because everyone refers to the same expectations.

Version Your Deployments and Tie Them to Invalidation

For teams with frequent releases, align deployment steps with cache actions:

• Deploy new assets first
• Then invalidate HTML or non-versioned resources
• Finally monitor hit rate and origin load

This reduces the chance that CDN pulls missing or old content.

Regularly Review Cache Efficiency

At intervals, check:

• Hit rate trends
• Top URL groups by origin bandwidth
• Cache misses caused by headers, query strings, or rule mismatches

When you see “unexpectedly hot” origin URLs, it’s usually a sign that caching rules don’t match the actual traffic patterns.

Conclusion: Build a Cache Strategy, Then Implement It Precisely

Good Tencent Cloud CDN cache configuration is less about one setting and more about a coherent strategy: categorize content, control caching through clear headers, write narrow and ordered cache rules, handle query strings and headers deliberately, and validate with real metrics. When these pieces align, you get a CDN that is fast without being fragile—and predictable updates without constant firefighting.

If you’re improving an existing setup, begin with static assets and HTML separately, then refine query-string and bypass rules for dynamic endpoints. Once you can explain why a request is cached (or not cached), you’re in control. That’s the true best practice.