feat: working on chapter 11

Author: lmammino

11-advanced-recipes/04-batching-and-caching/.gitignore

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+sales/

11-advanced-recipes/04-batching-and-caching/README.md

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+# 04-batching-and-caching
+
+This sample shocases how asynchronous batching and caching work.
+
+## Dependencies
+
+This example requires you to install some third-party dependencies from npm.
+
+If you have `pnpm` installed, you can do that with:
+
+```bash
+pnpm install
+```
+
+Alternatively, if you prefer to use another package manager, make sure to delete
+the `pnpm-lock.yaml` file before using it.
+
+If you want to use `npm`, you can run:
+
+```bash
+npm install
+```
+
+If you want to use `yarn`, you can run:
+
+```bash
+yarn install
+```
+
+## Run
+
+First, populate the database with some sample data:
+
+```
+node populateDb.js
+```
+
+The command above will create 100000 random sales transactions in the format:
+
+```
+{amount, product}
+```
+
+Next, to start the server, run:
+
+```
+node server.js
+```
+
+To test the server with multiple concurrent request, simply run:
+
+```
+autocannon 'http://localhost:8000/?product=book'
+```
+
+In the file `server.js`, try to swap between the various implementations of the
+`totalSales()` API to compare their performances. Please note that using the
+vanilla implementation (`totalSales`).
+
+```
+import { totalSales } from './totalSales.js'
+// import {totalSales} from './totalSalesBatch.js'
+// import {totalSales} from './totalSalesCache.js'
+```
+
+NOTE: remember to restart the server after changing the implementation before
+running the benchmark again.

11-advanced-recipes/04-batching-and-caching/package.json

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+{
+  "name": "04-batching-and-caching",
+  "version": "1.0.0",
+  "description": "This sample showcases how asynchronous batching and caching work",
+  "type": "module",
+  "scripts": {},
+  "engines": {
+    "node": ">=23"
+  },
+  "engineStrict": true,
+  "keywords": [],
+  "author": "Luciano Mammino and Mario Casciaro",
+  "license": "MIT",
+  "dependencies": {
+    "level": "^10.0.0",
+    "nanoid": "^5.1.5"
+  },
+  "devDependencies": {
+    "autocannon": "^8.0.0"
+  }
+}