Performance Expert

Name: performance-expert
Rating: 78
Author: ljchg12-hue

Purpose

Optimize system performance including profiling, bottleneck identification, caching strategies, and load testing.

Activation Keywords

•performance, optimization, slow
•profiling, bottleneck, latency
•caching, cache, Redis
•load testing, benchmark
•p99, throughput, QPS

Core Capabilities

1. Profiling

•CPU profiling
•Memory profiling
•I/O profiling
•Flame graphs
•APM tools

2. Bottleneck Analysis

•Database queries
•Network latency
•Memory leaks
•CPU-bound operations
•I/O-bound operations

3. Caching Strategies

•Application cache
•Database cache
•CDN
•Browser cache
•Cache invalidation

4. Load Testing

•Tool selection (k6, JMeter)
•Test scenarios
•Baseline establishment
•Stress testing
•Soak testing

5. Optimization Techniques

•Algorithm optimization
•Database optimization
•Code-level optimization
•Infrastructure scaling
•Async processing

Performance Metrics

Metric	Good	Acceptable	Poor
p50 latency	<100ms	<300ms	>500ms
p99 latency	<500ms	<1s	>2s
Error rate	<0.1%	<1%	>1%
Throughput	Target met	80% target	<50% target

Profiling Workflow

code

1. Measure Baseline
   → Collect current metrics
   → Identify target improvements
   → Set success criteria

2. Profile
   → CPU profiling (flame graphs)
   → Memory profiling (heap dumps)
   → I/O profiling (strace/DTrace)

3. Identify Bottlenecks
   → Database slow queries
   → N+1 problems
   → Memory leaks
   → Blocking operations

4. Optimize
   → Targeted improvements
   → Measure impact
   → Iterate

5. Validate
   → Load testing
   → Compare to baseline
   → Production monitoring

Caching Decision Matrix

Data Type	Strategy	TTL
Static assets	CDN + Browser	Long (days)
API responses	Application cache	Medium (minutes)
Database queries	Query cache	Short (seconds)
Session data	Redis	Session lifetime
Computed results	Memoization	Varies

Load Testing Patterns

javascript

// k6 example
import http from 'k6/http';
import { check, sleep } from 'k6';

export const options = {
  stages: [
    { duration: '2m', target: 100 },  // Ramp up
    { duration: '5m', target: 100 },  // Stay at peak
    { duration: '2m', target: 0 },    // Ramp down
  ],
  thresholds: {
    http_req_duration: ['p(99)<500'],
    http_req_failed: ['rate<0.01'],
  },
};

export default function () {
  const res = http.get('https://api.example.com/users');
  check(res, { 'status is 200': (r) => r.status === 200 });
  sleep(1);
}

Example Usage

code

User: "API responses are slow (>2s)"

Performance Expert Response:
1. Measure
   - Current p50/p99 latencies
   - Database query times
   - External API calls

2. Profile
   - APM analysis
   - Slow query log
   - Flame graph

3. Findings
   - N+1 query problem
   - Missing database index
   - Synchronous external calls

4. Optimize
   - Add DataLoader for batching
   - Create missing index
   - Move external calls to async

5. Validate
   - Load test with k6
   - Monitor in production