SkillVaultskills Browse all 500 skills

Performance · Version 1.3.0 · Reviewed 2026-08-02

CDN Cache Strategy Advisor

Locate and remove the dominant bottleneck in cache key design and purge strategy with evidence, explicit trade-offs, and a verification plan.

4 method steps 6 documented failure modes 5 diagnostic checks 7 quality gates

Designs cache keys, TTLs, purge strategy, and origin shielding for correct and effective edge caching.

₹149 one-time

Get this skill archive

What this skill helps you do

  • Cache key design
  • Purge strategy
  • Origin protection

How CDN Cache Strategy Advisor works

You provide

Read/write ratio, staleness tolerance, and current keys

It inspects

Invalidation path and key completeness for cache key design

It decides

A purge strategy design with stampede protection

You verify

System stays correct with the cache disabled entirely

What it checks first

CDN Cache Strategy Advisor designs cache keys, TTLs, purge strategy, and origin shielding for correct and effective edge caching. Use it when the work involves Cache key design, Purge strategy, Origin protection.

  1. Hit rate together with the cost of a miss, because a low hit rate on a cheap computation does not matter.
  2. Whether invalidation is event-driven or purely TTL-based, which decides the maximum staleness.
  3. Key cardinality and value size distribution, since a few large values can dominate memory.
  4. Eviction policy relative to access pattern, and whether evictions are happening at all.
  5. Whether the cache is a performance optimization or has silently become a correctness dependency.

Failure modes it recognizes

  • Cache stampede when a popular key expires and every concurrent request recomputes it.
  • Stale data served indefinitely because the invalidation path silently failed.
  • A cached negative result (empty or error) persisting after the underlying data becomes available.
  • Cache key collisions from omitting a dimension such as locale, tenant, or permission scope.
  • Memory pressure evicting hot keys because one workload writes large cold values.
  • The application failing entirely when the cache is unavailable, because the fallback path was never tested.

Answers it will reject

  • Caching to hide a slow query rather than fixing the query, which doubles the systems to reason about.
  • Using a single global TTL for data with different volatility.
  • Caching personalized responses on a shared layer, which is a data-leak vulnerability, not a performance win.
  • Increasing TTL to raise hit rate without deciding the acceptable staleness for the business.

Decision rules it applies

  • Choose the invalidation strategy before the caching strategy — invalidation is the hard part.
  • Protect against stampede with a lock, a stale-while-revalidate window, or jittered expiry.
  • Include every dimension that changes the response in the cache key, especially identity and permission.
  • The system must remain correct with an empty cache; verify by testing with the cache disabled.

Evidence it asks for

  • Report hit rate, miss latency, eviction rate, and memory usage together — one alone is not interpretable.
  • Load-test with a cold cache to confirm the origin survives a full flush.
  • Log staleness age on cache hits so unexpected staleness becomes visible.

The method inside

  1. Map the artifact, actors, boundaries, and invariants relevant to cache key design.
  2. Trace concrete failure or abuse paths for purge strategy; do not report checklist items without a mechanism.
  3. Prioritize origin protection findings by impact, likelihood, confidence, and cost of correction.
  4. Recommend the smallest defensible change, then define how an independent reviewer can verify it.

Deliverables

  • Cache key design assessment
  • Purge strategy decision and action plan
  • Origin protection verification checklist

Evidence requirements

  • Profiles, traces, timings, resource metrics, and workload shape
  • Baseline and target percentile
  • Environment, concurrency, and payload details

Quality gates

  • Every material claim traces to supplied evidence or is labeled as a hypothesis.
  • The response follows the declared deliverable contract.
  • No execution, access, measurement, or verification is invented.
  • Secrets and personal data are redacted rather than repeated.
  • The user receives a concrete independent verification step.
  • The relevant failure modes in this domain were considered rather than only the reported symptom.
  • No listed anti-pattern was recommended as a solution.

Example task

Input

Our CDN hit rate is 40 percent and we occasionally serve one customer content belonging to another.

Expected output

Both symptoms come from the cache key. Including a cookie or a unique header fragments the cache and destroys hit rate, and omitting a dimension that changes the response causes cross-customer leakage. Enumerate what varies the response and encode exactly that...

Boundaries and compatibility

Ideal for

  • Cache key design: produce a decision or artifact grounded in supplied evidence.
  • Purge strategy: produce a decision or artifact grounded in supplied evidence.
  • Origin protection: produce a decision or artifact grounded in supplied evidence.

Out of scope

  • Optimizing without a baseline
  • Using averages where tail latency determines experience

Agent compatibility

  • GitHub Copilot custom agents
  • Claude Agent Skills / SKILL.md
  • Any instruction-following chat model

Tool policy: Advisory by default. No tools are assumed. If the host provides tools, use read-only evidence gathering unless the user explicitly approves a scoped write or execution action.