---
id: secondsky/claude-skills/cloudflare-workers-performance
version: "dfb5a494"
license: MIT
install: manual
updated: 2026-07-25
---

# cloudflare-workers-performance — Master performance tuning for Cloudflare Workers through CPU optimization, memory management, and strategic caching. Learn to profile hot paths, stream large payloads, batch operations, and minimize cold starts while staying within platform limits.

Publisher: secondsky · Stars: 196 · Updated: 2026-07-25

Install (manual): `git clone https://github.com/secondsky/claude-skills`

## SKILL.md

# Cloudflare Workers Performance Optimization

Techniques for maximizing Worker performance and minimizing latency.

## Quick Wins

```typescript
// 1. Avoid unnecessary cloning
// ❌ Bad: Clones entire request
const body = await request.clone().json();

// ✅ Good: Parse directly when not re-using body
const body = await request.json();

// 2. Use streaming instead of buffering
// ❌ Bad: Buffers entire response
const text = await response.text();
return new Response(transform(text));

// ✅ Good: Stream transformation
return new Response(response.body.pipeThrough(new TransformStream({
  transform(chunk, controller) {
    controller.enqueue(process(chunk));
  }
})));

// 3. Cache expensive operations
const cache = caches.default;
const cached = await cache.match(request);
if (cached) return cached;
```

## Critical Rules

1. **Stay under CPU limits** - 10ms (free), 30ms (paid), 50ms (unbound)
2. **Minimize cold starts** - Keep bundles < 1MB, avoid dynamic imports
3. **Use Cache API** - Cache responses at the edge
4. **Stream large payloads** - Don't buffer entire responses
5. **Batch operations** - Combine multiple KV/D1 calls

## Top 10 Performance Errors

| Error | Symptom | Fix |
|-------|---------|-----|
| CPU limit exceeded | Worker terminated | Optimize hot paths, use streaming |
| Cold start latency | First request slow | Reduce bundle size, avoid top-level await |
| Memory pressure | Slow GC, timeouts | Stream data, avoid large arrays |
| KV latency | Slow reads | Use Cache API, batch reads |
| D1 slow queries | High latency | Add indexes, optimize SQL |
| Large bundles | Slow cold starts | Tree-shake, code split |
| Blocking operations | Request timeouts | Use Promise.all, streaming |
| Unnecessary cloning | Memory spike | Only clone when needed |
| Missing cache | Repeated computation | Implement caching layer |
| Sync operations | CPU spikes | Use async alternatives |

## CPU Optimization

### Profile Hot Paths

```typescript
async function profiledHandler(request: Request): Promise<Response> {
  const timing: Record<string, number> = {};

  const time = async <T>(name: string, fn: () => Promise<T>): Promise<T> => {
    const start = Date.now();
    const result = await fn();
    timing[name] = Date.now() - start;
    return result;
  };

  const data = await time('fetch', () => fetchData());
  const processed = await time('process', () => processData(data));
  const response = await time('serialize', () => serialize(processed));

  console.log('Timing:', timing);
  return new Response(response);
}
```

### Optimize JSON Operations

```typescript
// For large JSON, use streaming parser
import { JSONParser } from '@streamparser/json';

async function parseStreamingJSON(stream: ReadableStream): Promise<unknown[]> {
  const parser = new JSONParser();
  const results: unknown[] = [];

  parser.onValue = (value) => results.push(value);

  for await (const chunk of stream) {
    parser.write(chunk);
  }

  return results;
}
```

## Memory Optimization

### Avoid Large Arrays

```typescript
// ❌ Bad: Loads all into memory
const items = await db.prepare('SELECT * FROM items').all();
const processed = items.results.map(transform);

// ✅ Good: Process in batches
async function* batchProcess(db: D1Database, batchSize = 100) {
  let offset = 0;
  while (true) {
    const { results } = await db
      .prepare('SELECT * FROM items LIMIT ? OFFSET ?')
      .bind(batchSize, offset)
      .all();

    if (results.length === 0) break;

    for (const item of results) {
      yield transform(item);
    }
    offset += batchSize;
  }
}
```

## Caching Strategies

### Multi-Layer Cache

```typescript
interface CacheLayer {
  get(key: string): Promise<unknown | null>;
  set(key: string, value: unknown, ttl?: number): Promise<void>;
}

// Layer 1: In-memory (request-scoped)
const memoryCache = new Map<string, unknown>();

// Layer 2: Cache API (edge-local)
const edgeCache: CacheLayer = {
  async get(key) {
    const response = await caches.default.match(new Request(`https://cache/${key}`));
    return response ? response.json() : null;
  },
  async set(key, value, ttl = 60) {
    await caches.default.put(
      new Request(`https://cache/${key}`),
      new Response(JSON.stringify(value), {
        headers: { 'Cache-Control': `max-age=${ttl}` }
      })
    );
  }
};

// Layer 3: KV (global)
// Use env.KV.get/put
```

## Bundle Optimization

```typescript
// 1. Tree-shake imports
// ❌ Bad
import * as lodash from 'lodash';

// ✅ Good
import { debounce } from 'lodash-es';

// 2. Lazy load heavy dependencies
let heavyLib: typeof import('heavy-lib') | undefined;

async function getHeavyLib() {
  if (!heavyLib) {
    heavyLib = await import('heavy-lib');
  }
  return heavyLib;
}
```

## When to Load References

Load specific references based on the task:

- **Optimizing CPU usage?** → Load `references/cpu-optimization.md`
- **Memory issues?** → Load `references/memory-optimization.md`
- **Implementing caching?** → Load `references/caching-strategies.md`
- **Reducing bundle size?** → Load `references/bundle-optimization.md`
- **Cold start problems?** → Load `references/cold-starts.md`

## Templates

| Template | Purpose | Use When |
|----------|---------|----------|
| `templates/performance-middleware.ts` | Performance monitoring | Adding timing/profiling |
| `templates/caching-layer.ts` | Multi-layer caching | Implementing cache |
| `templates/optimized-worker.ts` | Performance patterns | Starting optimized worker |

## Scripts

| Script | Purpose | Command |
|--------|---------|---------|
| `scripts/benchmark.sh` | Load testing | `./benchmark.sh <url>` |
| `scripts/profile-worker.sh` | CPU profiling | `./profile-worker.sh` |

## Resources

- Performance: https://developers.cloudflare.com/workers/platform/performance/
- Limits: https://developers.cloudflare.com/workers/platform/limits/
- Caching: https://developers.cloudflare.com/workers/runtime-apis/cache/


[View on SkillFed](https://skillfed.io/secondsky/claude-skills/cloudflare-workers-performance) · [View on GitHub](https://github.com/secondsky/claude-skills)