document sharding

Author: notunderctrl

apps/website/docs/guide/08-advanced/03-sharding-your-bot.mdx

@@ -1,3 +1,66 @@
 ---
-title: Sharding your bot
+title: Sharding Your Discord Bot
 ---
+
+Sharding is a method of splitting your bot into multiple processes, or
+"shards". This is useful for large bots that have a lot of guilds, as
+it allows you to distribute the load across multiple processes.
+Discord actually requires sharding for bots in more than 2,500 guilds,
+so understanding how to implement it is crucial as your bot grows.
+
+Sharding is a built-in feature of discord.js, and CommandKit does not
+alter the way sharding works. While this guide covers how to shard
+your bot using CommandKit, you can learn more about sharding in
+discord.js by checking out the
+[discord.js guide](https://discordjs.guide/sharding).
+
+## When to use sharding
+
+You should consider implementing sharding in the following scenarios:
+
+- Your bot is in, or approaching, 2,500 guilds (required by Discord)
+- You're experiencing memory or performance issues with a single
+  process
+- You want to distribute your bot's workload across multiple
+  cores/machines
+- You're considering scaling your bot in the future
+
+## Creating a sharding manager file
+
+You can simply create a new file in your source directory named
+`sharding-manager.ts` (or `sharding-manager.js` if you're using
+JavaScript) and CommandKit will automatically detect it and use it as
+the sharding manager. This file will be responsible for creating the
+shards and managing them.
+
+```ts title="src/sharding-manager.ts"
+import { ShardingManager } from 'discord.js';
+import { join } from 'node:path';
+
+process.loadEnvFile('./.env');
+
+const manager = new ShardingManager(
+  join(import.meta.dirname, 'index.js'),
+  {
+    token: process.env.DISCORD_TOKEN,
+    totalShards: 2,
+    mode: 'worker',
+  },
+);
+
+manager.on('shardCreate', (shard) =>
+  console.log(`Launched shard ${shard.id}`),
+);
+
+await manager.spawn();
+```
+
+:::info
+
+If you're confused about `index.js` being used, this is an
+autogenerated entrypoint file that sets up the CommandKit environment.
+When running `commandkit start` or `commandkit dev`, CommandKit
+automatically detects the entrypoint file (either
+`sharding-manager.js` or `index.js`) and loads it.
+
+:::