The Smart Router: How Your API Becomes a Traffic Director

Here's where the magic happens - your API server becomes like a smart traffic controller that knows exactly where every piece of data lives!

The Routing Logic:

function getShardForUser(userId) {
  if (userId >= 1 && userId <= 500000) {
    return 'shard-1.<TopicPreview slug="database">database</TopicPreview>.com';
  } else if (userId >= 500001 && userId <= 1000000) {
    return 'shard-2.database.com';
  }
}

const userShard = getShardForUser(userId);
const userData = await userShard.query('SELECT * FROM users WHERE id = ?', [userId]);

The Beautiful Transparency: Users have no idea their data might be in California while their friend's data is in New York. Your API handles all the complexity!

Load Balancing Magic: If one shard gets too hot, you can move partitions around:

• Take the "heavy users" partition from Shard 1
• Move it to Shard 3 which has more capacity
• Update your routing logic
• Users never notice!

Key Insight: "Your API server becomes the intelligent middleman that makes multiple databases look like one seamless system to your users."