adds redis notes

src/express/redis.md

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+# Redis
+
+## Install Redis
+
+There are a few ways of
+[installing Redis itself](https://redis.io/docs/latest/operate/oss_and_stack/install/).
+
+::: [TIP]
+
+Note that Redis is a lightweight version, whereas Redis Stack contains more
+features.
+
+:::
+
+If you are using Docker, you should be able to access Redis without explicitly
+running it. If you have installed natively, you may need to run it:
+
+::: code-group
+
+```bash
+redis-server
+```
+
+```bash
+# if using redis stack
+redis-stack-server
+```
+
+:::
+
+## Install Redis Client
+
+There is a client library for Node.js which makes developing against a Redis
+database much easier.
+
+To install it, run
+
+```bash
+npm install redis
+```
+
+in your Node project.
+
+## Basic operations
+
+At its core, Redis is concerned with setting and getting key/value pairs.
+
+```js
+// Import the redis package
+import redis from 'redis'
+
+// Create a Redis client instance
+const r = redis.createClient({
+  url: 'redis://localhost:6379'
+})
+
+// Handle connection errors
+r.on('error', err => console.log('Redis Client Error', err))
+
+// Connect the client
+await r.connect()
+
+// Basic Redis commands (set and get)
+await r.set('mykey', 'Hello Redis') // Set a key-value pair
+const value = await r.get('mykey') // Get the value of the key
+console.log('mykey:', value)
+
+// Close the connection when done
+await r.quit()
+```
+
+## Working with JSON
+
+Redis can store JSON data without stringifying it.
+
+```js
+// Create a JSON object to store in Redis
+const user = {
+  id: 'user:1001',
+  name: 'Jane Doe',
+  age: 25,
+  email: '[email protected]',
+  address: {
+    city: 'London',
+    country: 'UK'
+  }
+}
+
+// Set the JSON object using RedisJSON (json.set)
+await r.json.set(user.id, '$', user)
+
+const storedUser = await r.json.get(user.id)
+```
+
+The keys can be manipulated individually:
+
+```js
+// Update the age field
+await r.json.set('user:1001', '$.age', 26)
+
+// Read the email field
+const userEmail = await r.json.get('user:1001', { path: '$.email' })
+```
+
+## Search index
+
+We can create a search index which allows us to implement full text search.
+
+```js
+// Create a new search index using RedisSearch
+await r.ft.create('userIndex'
+  {
+    '$.name': {
+      type: 'TEXT', // Full-text search over the 'name' field
+      sortable: true // Allows sorting by this field
+    },
+    '$.age': {
+      type: 'NUMERIC', // Numeric field to support range queries
+    }
+  },
+  {
+    ON: 'JSON', // We're indexing JSON documents
+    PREFIX: 'user:' // Only index keys that start with 'user:'
+  }
+)
+```
+
+Now we can search for users by name or age.
+
+```js
+const result1 = await r.ft.search('userIdx', '@name:Jane')
+const result2 = await r.ft.search('userIdx', '@age:[25 35]')
+```