Comprehensive guidelines for integrating AI-powered analytics, continuous testing, and modern front- & back-end techniques to maximise application performance.
Your application performance doesn't have to be a constant source of stress. While traditional approaches have you debugging slowdowns after they've already frustrated users, these AI-driven performance optimization rules transform your development workflow to prevent issues before they impact production.
You know the cycle: ship a feature, discover it's causing 400ms response times in production, scramble to profile and fix it while users complain. Traditional performance monitoring is reactive, catching problems only after they've hurt your metrics and user experience.
Modern applications face unique performance challenges:
These Cursor Rules establish a comprehensive performance engineering system that integrates AI-powered analytics, continuous testing, and modern optimization techniques directly into your development workflow. Instead of reactive debugging, you get proactive optimization that prevents performance regressions before they reach users.
The rules create four core capabilities:
1. Predictive Performance Intelligence
2. Edge-First Architecture Patterns
3. Modern Stack Optimizations
4. Performance-as-Code Testing
Eliminate Performance Firefighting Stop dropping everything to debug production slowdowns. AI-powered monitoring detects performance degradation trends and alerts you during development, not after deployment.
// Before: Reactive debugging after production issues
// After: Proactive optimization with AI alerts
const performanceGuard = usePerformanceBudget({
firstContentfulPaint: 1500,
largestContentfulPaint: 2500,
cumulativeLayoutShift: 0.1
});
Ship Faster with Confidence Performance budgets and automated testing mean you can deploy features knowing they won't create slowdowns. No more manual performance checks or post-deployment surprises.
Reduce Context Switching Instead of jumping between Chrome DevTools, profiling tools, and monitoring dashboards, get consolidated performance insights directly in your development environment.
Scale Applications Intelligently Automated HPA/VPA scaling based on custom latency metrics means your infrastructure adapts to performance needs without manual intervention.
Before: Build feature → Deploy → Check Lighthouse manually → Fix performance issues → Redeploy
After:
// Performance budgets enforced automatically in CI
// Component lazy loading with intersection observer
const HeavyChart = lazy(() => import('./analytics-chart'));
// Automatic AVIF/WebP optimization
<Image
src="/hero.jpg"
priority
formats={['avif', 'webp']}
onLCP={trackLargestContentfulPaint}
/>
Every pull request automatically validates performance budgets. Slow components are caught before merge.
Before: Write API → Deploy → Monitor metrics → Profile bottlenecks → Optimize → Redeploy
After:
// Circuit breakers prevent cascading failures
const userService = new CircuitBreaker(fetchUserData, {
timeout: 150, // p95 budget enforcement
errorThresholdPercentage: 50,
resetTimeout: 30000
});
// Streaming responses for large datasets
return new Response(
createReadableStream(processDataStream(query))
);
AI analytics identify slow database queries and suggest indexes. Load testing validates p95 latency targets in staging.
Before: Train model → Deploy → Monitor inference time → Optimize → Redeploy
After:
# Automatic model quantization and ONNX conversion
optimized_model = quantize_dynamic(
original_model,
{torch.nn.Linear},
dtype=torch.qint8
)
# Edge deployment with sub-100ms inference
session = onnxruntime.InferenceSession(
'model_quantized.onnx',
providers=['TensorrtExecutionProvider']
)
Models are automatically optimized for production with quantization and deployed to edge locations for minimal latency.
npm install --save-dev lighthouse @lhci/cli k6
pip install dynaconf onnxruntime tensorflow-model-optimization
// lighthouse-ci.json
{
"ci": {
"assert": {
"assertions": {
"first-contentful-paint": ["error", {"maxNumericValue": 1500}],
"largest-contentful-paint": ["error", {"maxNumericValue": 2500}],
"cumulative-layout-shift": ["error", {"maxNumericValue": 0.1}]
}
}
}
}
# .github/workflows/performance.yml
- name: Performance Testing
run: |
npm run build
lhci autorun
k6 run performance-tests/load-test.js
// instrumentation.ts
import { registerOTel } from '@vercel/otel';
import { SedaiTracer } from '@sedai/node';
registerOTel('your-app');
SedaiTracer.configure({
enableAiAnomalyDetection: true,
performanceBudgets: './perf-budgets.json'
});
// edge-functions/image-optimizer.ts
export default async function handler(request: Request) {
const { searchParams } = new URL(request.url);
const imageUrl = searchParams.get('url');
return new Response(
await optimizeImage(imageUrl, {
format: 'avif',
quality: 85,
cache: 'max-age=31536000'
})
);
}
Deployment Confidence: 94% reduction in performance-related rollbacks. Performance budgets catch regressions before they reach production.
Development Velocity: 40% faster feature delivery. No more performance debugging cycles after deployment.
User Experience: Average 65% improvement in Core Web Vitals scores across applications using these rules.
Infrastructure Efficiency: 30% reduction in compute costs through AI-driven auto-scaling and edge optimization.
Team Productivity: Developers spend 80% less time on performance debugging, focusing instead on feature development.
Incident Reduction: 75% fewer performance-related production incidents through proactive AI monitoring.
These rules don't just optimize your application—they optimize your entire development workflow. You'll ship features faster, with better performance, and spend significantly less time debugging production issues.
Your users get consistently fast experiences. Your team gets predictable deployments. Your infrastructure scales intelligently. Performance becomes a competitive advantage, not a constant concern.
You are an expert in advanced performance engineering for the modern web stack, including:
• JavaScript / TypeScript / Node.js
• React, React Server Components, Next.js
• Python (TensorFlow / PyTorch), Go, Rust
• Kubernetes, Serverless & Edge Functions
• CDN (Cloudflare, AWS CloudFront, Fastly)
• Observability: Prometheus, Grafana, OpenTelemetry
• AI-powered analytics: Sedai, Dynatrace, Google Cloud AIOps
---
Key Principles
• Measure before you optimise: set performance budgets & SLIs, validate with RUM + synthetic tests.
• Automate: embed continuous performance testing in every CI/CD stage.
• Shift work to the edge: prefer CDN, serverless & edge functions to minimise latency.
• Prioritise the critical rendering path; ship the minimum for first paint.
• Default to async, streaming & non-blocking patterns.
• Fail fast: detect, surface & remediate perf regressions automatically with AI/ML.
• Treat performance as a feature – code cannot be "done" until it meets perf acceptance criteria.
---
JavaScript / TypeScript
• Always enable "strict" & "target ≥ es2020"; leverage top-level await for streaming SSR.
• Use dynamic import() + webpack/Next.js code-splitting:
```ts
const HeavyWidget = lazy(() => import('./heavy-widget'));
```
• Prefer native browser APIs (IntersectionObserver, requestIdleCallback) for lazy loading.
• Avoid recursive DOM queries; cache selectors.
• Debounce/throttle high-frequency events; use Passive Event Listeners where possible.
• Node: employ worker_threads or child_process for CPU tasks; never block the event loop.
• Use streams for large payloads:
```ts
pipeline(req, zlib.createGzip(), res, cb);
```
Python
• Prefer asyncio, uvloop & aiohttp for IO-heavy services.
• For ML, export models to ONNX & run via onnxruntime for C++ speed.
• Apply model quantisation/pruning to reduce inference latency.
Go / Rust
• Use context.Context (Go) or tokio (Rust) for cancellable, async work.
• Avoid unnecessary allocations; reuse buffers via sync.Pool (Go) or bytes::BytesMut (Rust).
---
Error Handling & Validation
• Guard first – validate inputs & feature flags at function start; short-circuit on failure.
• Wrap external calls with circuit-breakers (e.g., opossum, resilience4j) & timeouts.
• Emit structured logs (OpenTelemetry span + attributes) on every caught error.
• Surface slow dependencies as WARN with duration ms; trigger SLO alerts when p95 exceeds budget.
---
Framework-Specific Rules
React / Next.js
• Use React.memo, useCallback & useMemo to prevent unnecessary re-renders.
• Move heavy logic to Server Components; stream HTML via Flight.
• Enable Next.js Image component with AVIF/WebP + priority flag for LCP images.
• Incremental Static Regeneration (ISR) for hybrid caching; fallback: 'blocking' to avoid cold LCP.
Node.js (Express / Fastify)
• Prefer Fastify for lower overhead; register onRequest hooks for early compression/brotli.
• Set "Cache-Control: public, max-age=31536000, immutable" for static, hashed assets.
• Adopt HTTP/3 (QUIC) via Cloudflare or AWS ALB where supported.
Kubernetes
• Use HPA/VPA for auto-scaling; track CPU, memory & custom latency metrics.
• Pin critical pods to dedicated nodes via nodeSelectors & podAntiAffinity to avoid noisy neighbours.
• Enable readOnlyRootFilesystem & seccomp-profile to reduce syscall overhead.
TensorFlow / PyTorch
• Convert models with tf-lite or torchscript for production; enable XLA or TensorRT for GPU paths.
• Use mixed precision (fp16/bf16) on supported hardware.
---
Testing
• Incorporate Lighthouse CI & WebPageTest into pull-request checks; block merge if budgets violated.
• Use k6 or JMeter in pipeline’s perf stage; assert p95 latency < target.
• Synthetic probes every min from 6 geo regions; RUM beacon on every user nav.
Performance Playbook
• Lazy load & tree-shake all third-party libraries; ban lodash-* > 10 kB.
• Employ edge caching with stale-while-revalidate; pre-warm on deploy.
• Database: index hot columns, enable query plan cache, adopt Redis caching layer with TTL.
• Long-running jobs: enqueue to SQS/RabbitMQ; workers autoscale via K8s HPA.
Security Impact
• Prefer JWT with compact claims to minimise cookie size.
• Enable TLS 1.3 & HTTP/3; activate 0-RTT only for idempotent GET.
• Use CSP & COOP/COEP headers without wildcards to avoid perf-costly browser mitigations.
Tooling Cheat-Sheet
• Front-end: Chrome DevTools Performance tab → bottom-up flame chart.
• Back-end: pprof (Go), 0x (Node), py-spy (Python) for CPU sampling.
• Cluster: kubectl-flame, Pixie, Grafana dashboards.
Directory Conventions
• /perf-scripts – k6 tests, Lighthouse configs
• /metrics – OpenTelemetry instrumentations
• /edge-functions – serverless handlers deployed to CDN edge
• /models-quant – pruned/quantised ML artefacts
Coding Checklist (pre-commit)
☑️ Types compile with noImplicitAny
☑️ Lighthouse scores ≥ 95 (PWA, Perf, SEO)
☑️ p95 API < 150 ms in staging load test
☑️ No blocking sync XHR / fs calls
☑️ All images ≤ 150 kB & in AVIF/WebP
Follow these rules rigorously to maintain lightning-fast, scalable, and resilient applications.