MySQL connection with mysql2 in Node.js - Performance & Optimization

Performance: MySQL connection with mysql2

MEDIUM IMPACT

This affects the initial page or API response load time by how quickly the database connection is established and queries are executed.

Connecting to MySQL and running queries in a Node.js app

Node.js

import mysql from 'mysql2/promise';
const pool = mysql.createPool({host: 'localhost', user: 'root', database: 'test', waitForConnections: true, connectionLimit: 10});
async function getUsers() {
  const [rows] = await pool.query('SELECT * FROM users');
  return rows;
}

Reuses connections from a pool asynchronously, reducing connection overhead and avoiding blocking.

📈 Performance GainReduces connection overhead by up to 90%, non-blocking queries improve throughput and lower latency

Connecting to MySQL and running queries in a Node.js app

Node.js

const mysql = require('mysql2');
const connection = mysql.createConnection({host: 'localhost', user: 'root', database: 'test'});
connection.query('SELECT * FROM users', (err, results) => {
  if (err) throw err;
  console.log(results);
});
connection.end();

Creates a new connection for every query, blocking the event loop and causing delays under load.

📉 Performance CostBlocks event loop during connection setup, triggers multiple TCP handshakes, increases response time by 100-200ms per query

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Single connection per query	N/A	N/A	N/A	[X] Bad
Connection pool with async queries	N/A	N/A	N/A	[OK] Good

Rendering Pipeline

Database connection and query execution happen before the server sends the response, affecting how fast the browser receives content.

→Server Processing

→Network Request

→First Byte Time

⚠️ BottleneckConnection setup and synchronous query execution block server event loop

Core Web Vital Affected

LCP

This affects the initial page or API response load time by how quickly the database connection is established and queries are executed.

Optimization Tips

1Always use connection pooling to reuse MySQL connections.

2Use async/await queries to avoid blocking the Node.js event loop.

3Avoid creating a new connection for every query to reduce latency.

Performance Quiz - 3 Questions

What is the main performance benefit of using a connection pool with mysql2 in Node.js?

A It compresses the database responses to save bandwidth

B It automatically caches query results in the browser

C Reusing existing connections reduces connection overhead and latency

D It prevents SQL injection attacks

DevTools: Network

How to check: Open DevTools Network panel, observe Time to First Byte (TTFB) for API calls that query MySQL

What to look for: High TTFB indicates slow database response; lower TTFB with pooling means better performance