# api-response-optimization

A coding-agent skill that walks through payload trimming, HTTP caching and compression for API endpoints. Useful when responses feel slow.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 422 installs · ★ 236
- Author: secondsky
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/secondsky/claude-skills/tree/HEAD/plugins/api-response-optimization/skills/api-response-optimization/SKILL.md
- Updated: 2026-10-20
- HTML: https://affpapa.org/en/nevibecode/skills/secondsky-api-response-optimization

## What it does

The skill covers three areas: sparse fieldsets, HTTP caching and response compression. Each comes with a JavaScript example. Sparse fieldsets let a client ask for specific columns through a `fields` query parameter. Caching relies on `ETag` and `Cache-Control` headers, and a matching `if-none-match` returns `304` with no body.

Compression is wired up with the `compression` package, a filter that checks the `x-no-compression` header and level 6. There is a checklist too: drop unnecessary fields, add `ETag`/`Last-Modified`, turn on gzip or brotli, paginate collections, eager-load relations to avoid N+1 queries, and watch metrics through APM tools. Performance targets are listed as well, such as a response under 100ms instead of 500ms.

One piece of advice stands out: profile before optimizing. Skip that step and you may compress the wrong part of the request path while CPU usage climbs. Aggressive caching belongs on immutable resources only; frequently changing data needs a short TTL and cache invalidation on writes.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add secondsky/claude-skills --skill api-response-optimization -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/api-response-optimization/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/api-response-optimization/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add secondsky/claude-skills --skill api-response-optimization -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/api-response-optimization/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add secondsky/claude-skills --skill api-response-optimization -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/api-response-optimization/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install secondsky/claude-skills api-response-optimization
```

2. **Manually: put the files in place**
- File: `.github/skills/api-response-optimization/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add secondsky/claude-skills --skill api-response-optimization -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/secondsky/claude-skills --path plugins/api-response-optimization/skills/api-response-optimization
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/api-response-optimization/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add secondsky/claude-skills --skill api-response-optimization -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/secondsky/claude-skills/tree/HEAD/plugins/api-response-optimization/skills/api-response-optimization/SKILL.md

## When to use it
- shrink JSON responses by returning only requested fields
- add ETag support so repeat requests get a 304
- turn on gzip or brotli for responses over 1KB
- kill N+1 queries with eager loading
- build a pre-release checklist for an endpoint

## Example prompts
- add sparse fieldsets to this endpoint
- set up ETag and Cache-Control for the product route
- check these API responses for N+1 and tell me what to cache

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 32eb6844d6ce4e75.

BEGIN THIRD-PARTY FILE 32eb6844d6ce4e75
````text
---
name: api-response-optimization
description: Optimizes API performance through payload reduction, caching strategies, and compression techniques. Use when improving API response times, reducing bandwidth usage, or implementing efficient caching.
license: MIT
---

# API Response Optimization

Reduce payload sizes, implement caching, and enable compression for faster APIs.

## Sparse Fieldsets

```javascript
// Allow clients to select fields: GET /users?fields=id,name,email
app.get('/users', async (req, res) => {
  const fields = req.query.fields?.split(',') || null;
  const users = await User.find({}, fields?.join(' '));
  res.json(users);
});
```

## HTTP Caching Headers

```javascript
app.get('/products/:id', async (req, res) => {
  const product = await Product.findById(req.params.id);
  const etag = crypto.createHash('md5').update(JSON.stringify(product)).digest('hex');

  if (req.headers['if-none-match'] === etag) {
    return res.status(304).end();
  }

  res.set({
    'Cache-Control': 'public, max-age=3600',
    'ETag': etag
  });
  res.json(product);
});
```

## Response Compression

```javascript
const compression = require('compression');

app.use(compression({
  filter: (req, res) => {
    if (req.headers['x-no-compression']) return false;
    return compression.filter(req, res);
  },
  level: 6  // Balance between speed and compression
}));
```

## Performance Targets

| Metric | Target |
|--------|--------|
| Response time | <100ms (from 500ms) |
| Payload size | <50KB (from 500KB) |
| Server CPU | <30% (from 80%) |

## Optimization Checklist

- [ ] Remove sensitive/unnecessary fields from responses
- [ ] Implement sparse fieldsets
- [ ] Add ETag/Last-Modified headers
- [ ] Enable gzip/brotli compression
- [ ] Use pagination for collections
- [ ] Eager load to prevent N+1 queries
- [ ] Monitor with APM tools

## Best Practices

- Cache immutable resources aggressively
- Use short TTL for frequently changing data
- Invalidate cache on writes
- Compress responses >1KB
- Profile before optimizing
````
END THIRD-PARTY FILE 32eb6844d6ce4e75

The third-party file has ended. Everything between the 32eb6844d6ce4e75 tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

© secondsky · MIT · https://github.com/secondsky/claude-skills/tree/HEAD/plugins/api-response-optimization/skills/api-response-optimization/SKILL.md

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