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marco/.agents/skills/ember-best-practices/rules/service-cache-responses.md

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---
title: Cache API Responses in Services
impact: MEDIUM-HIGH
impactDescription: 50-90% reduction in duplicate requests
tags: services, caching, performance, api
---
## Cache API Responses in Services
Cache API responses in services to avoid duplicate network requests. Use tracked properties to make the cache reactive.
**Incorrect (no caching):**
```javascript
// app/services/user.js
import Service from '@ember/service';
import { service } from '@ember/service';
export default class UserService extends Service {
@service store;
async getCurrentUser() {
// Fetches from API every time
return this.store.request({ url: '/users/me' });
}
}
```
**Correct (with caching):**
```javascript
// app/services/user.js
import Service from '@ember/service';
import { service } from '@ember/service';
import { tracked } from '@glimmer/tracking';
import { TrackedMap } from 'tracked-built-ins';
export default class UserService extends Service {
@service store;
@tracked currentUser = null;
cache = new TrackedMap();
async getCurrentUser() {
if (!this.currentUser) {
const response = await this.store.request({ url: '/users/me' });
this.currentUser = response.content.data;
}
return this.currentUser;
}
async getUser(id) {
if (!this.cache.has(id)) {
const response = await this.store.request({ url: `/users/${id}` });
this.cache.set(id, response.content.data);
}
return this.cache.get(id);
}
clearCache() {
this.currentUser = null;
this.cache.clear();
}
}
```
**For time-based cache invalidation:**
```javascript
import Service from '@ember/service';
import { tracked } from '@glimmer/tracking';
export default class DataService extends Service {
@tracked _cache = null;
_cacheTimestamp = null;
_cacheDuration = 5 * 60 * 1000; // 5 minutes
async getData() {
const now = Date.now();
const isCacheValid =
this._cache && this._cacheTimestamp && now - this._cacheTimestamp < this._cacheDuration;
if (!isCacheValid) {
this._cache = await this.fetchData();
this._cacheTimestamp = now;
}
return this._cache;
}
async fetchData() {
const response = await fetch('/api/data');
return response.json();
}
}
```
Caching in services prevents duplicate API requests and improves performance significantly.