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Performance · Version 1.5.0 · Reviewed 2026-08-02

API Response Caching Advisor

Locate and remove the dominant bottleneck in validator selection and vary correctness with evidence, explicit trade-offs, and a verification plan.

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

Designs HTTP caching with correct validators, vary headers, and invalidation for API responses.

₹99 one-time

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What this skill helps you do

  • Validator selection
  • Vary correctness
  • Invalidation

How API Response Caching Advisor works

You provide

Baseline measurements, workload shape, and the target

It inspects

Dominant cost mechanism behind validator selection

It decides

A vary correctness change ranked by impact and risk

You verify

Re-measure under representative load with guardrails

What it checks first

API Response Caching Advisor designs HTTP caching with correct validators, vary headers, and invalidation for API responses. Use it when the work involves Validator selection, Vary correctness, Invalidation.

  1. A measured baseline and the user-visible target, since optimization without both is guesswork.
  2. Whether the cost is CPU, memory, I/O wait, or lock contention — they have opposite fixes.
  3. The p99 path and how many round trips it contains.
  4. Whether the bottleneck moves after a change, which determines if the gain is real.

Failure modes it recognizes

  • Optimizing a component that is not on the critical path, producing no end-to-end change.
  • A garbage-collection pause misread as slow application code.
  • Memory pressure causing swapping, which presents as unpredictable latency spikes.
  • A micro-optimization that improves the benchmark and regresses the real workload.

Answers it will reject

  • Tuning configuration flags before profiling where time is actually spent.
  • Measuring in a warmed-up loop that does not resemble production access patterns.
  • Reporting an improvement without the guardrail metric that would show a shifted bottleneck.

Decision rules it applies

  • Profile before changing anything, and attribute cost to a specific phase.
  • Optimize the dominant cost first; everything else is rounding.
  • Re-measure under representative load and keep a guardrail metric.

Evidence it asks for

  • Capture a profile during the real workload rather than a synthetic benchmark.
  • Record allocation rate and pause time alongside latency.
  • Compare before and after at the same percentile, not at the mean.

The method inside

  1. Map the artifact, actors, boundaries, and invariants relevant to validator selection.
  2. Trace concrete failure or abuse paths for vary correctness; do not report checklist items without a mechanism.
  3. Prioritize invalidation 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

  • Validator selection assessment
  • Vary correctness decision and action plan
  • Invalidation 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

We want to cache API responses at the edge but responses differ per authenticated user.

Expected output

Per-user responses at a shared cache is a data-leak risk before it is a performance question. Cache only what is genuinely shared, split endpoints so public and personalized data are separate, and use private caching with validators for the rest...

Boundaries and compatibility

Ideal for

  • Validator selection: produce a decision or artifact grounded in supplied evidence.
  • Vary correctness: produce a decision or artifact grounded in supplied evidence.
  • Invalidation: 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.