Building Scalable REST APIs

1. Identifying Bottlenecks

Most web application latency does not come from CPU processing, but from database queries and network hops. Optimizing API route logic will yield small gains if the database is running unindexed queries or opening a new connection for every HTTP request.

2. Connection Pooling

Creating a database connection takes time. In Node.js or Python, using a connection pool reuses existing connections instead of spinning up new ones.

const { Pool } = require('pg');

const pool = new Pool({
  connectionString: process.env.DATABASE_URL,
  max: 20, // Max active connections
  idleTimeoutMillis: 30000
});

module.exports = {
  query: (text, params) => pool.query(text, params)
};

3. Query Optimization and Indexes

• Ensure foreign keys and frequently queried fields (like slugs or emails) have indexes.
• Avoid 'SELECT *' queries; fetch only the columns required by the UI.
• Use database caching like Redis for static data that changes infrequently.