1# Redis Recipe — Node.js — REFERENCE ONLY
2 
3## ioredis with Token Refresh
4 
5### npm Packages
6 
7```bash
8npm install ioredis @azure/identity
9```
10 
11### Cache Module
12 
13Create `src/cache.js`:
14 
15```javascript
16const Redis = require("ioredis");
17const { DefaultAzureCredential } = require("@azure/identity");
18 
19const credential = new DefaultAzureCredential();
20const TOKEN_SCOPE = "https://redis.azure.com/.default";
21// Redis ACL auth requires both username and token as password
22const REDIS_USERNAME = "default";
23const TOKEN_REFRESH_MARGIN = 5 * 60 * 1000; // 5 minutes in ms
24 
25let _client = null;
26let _tokenExpiry = 0;
27 
28async function getToken() {
29  const tok = await credential.getToken(TOKEN_SCOPE);
30  _tokenExpiry = tok.expiresOnTimestamp;
31  return tok.token;
32}
33 
34async function getRedisClient() {
35  const now = Date.now();
36  if (_client && now < _tokenExpiry - TOKEN_REFRESH_MARGIN) {
37    return _client;
38  }
39 
40  // Token expired or about to expire — create a new client with a fresh token
41  if (_client) {
42    _client.disconnect();
43    _client = null;
44  }
45 
46  const token = await getToken();
47  _client = new Redis({
48    host: process.env.REDIS_HOST,
49    port: parseInt(process.env.REDIS_PORT || "6380"),
50    tls: { servername: process.env.REDIS_HOST },
51    username: REDIS_USERNAME,
52    password: token,
53    lazyConnect: true,
54  });
55  await _client.connect();
56  return _client;
57}
58 
59module.exports = { getRedisClient };
60```
61 
62> ⚠️ Entra ID tokens expire in ~1 hour. `getRedisClient()` recreates the connection with a fresh token when the current one is within 5 minutes of expiry. Always call `getRedisClient()` before each operation rather than caching the client reference long-term.
63 
64### Usage
65 
66```javascript
67const { getRedisClient } = require("./cache");
68 
69app.get("/api/cached", async (req, res) => {
70  const client = await getRedisClient();
71  let value = await client.get("my-key");
72  if (!value) {
73    value = "computed-value";
74    await client.setex("my-key", 300, value); // TTL 5 minutes
75  }
76  res.json({ value });
77});
78```
79 
80## Files to Modify
81 
82| File | Action |
83|------|--------|
84| `src/cache.js` | Create — Redis client with token refresh |
85| `src/index.js` | Modify — use getRedisClient() |
86| `package.json` | Modify — add ioredis, @azure/identity |
87