Performance Expert Skill

Performance Expert

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

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

// 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

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

Agent Skills: Performance Expert

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Skill Files