The Database Connection Leak

This query function works perfectly in testing but will bring down production.

DatabaseNode.jsPerformance

The Code

This code passed code review and works in development. But it has a bug that will cause problems in production.

queries.js

javascript

1const { Pool } = require('pg');
2 
3const pool = new Pool({
4  max: 20,
5  connectionTimeoutMillis: 5000,
6});
7 
8async function getOrdersByUser(userId) {
9  const client = await pool.connect();
10 
11  try {
12    const orders = await client.query(
13      'SELECT * FROM orders WHERE user_id = $1',
14      [userId]
15    );
16 
17    const enrichedOrders = await Promise.all(
18      orders.rows.map(async (order) => {
19        const items = await client.query(
20          'SELECT * FROM order_items WHERE order_id = $1',
21          [order.id]
22        );
23        return { ...order, items: items.rows };
24      })
25    );
26 
27    return enrichedOrders;
28  } catch (error) {
29    console.error('Query failed:', error);
30    throw error;
31  }
32}
33 
34// This function will exhaust your connection pool.
35// The bug is subtle but devastating.
36// Can you spot it?

// need a hint?

Progressive Hints

0 of 3 revealed

Hint 1 locked

Hint 2 locked

Hint 3 locked

// ready for the answer?

Ready for the Solution?

Enter your email to get the full solution with explanation, the fix, and why this bug is so common.

// more challenges

Keep Debugging

easy3-5 min

The Event Listener Memory Leak

This WebSocket handler looks clean but will slowly consume all your memory.

hard10-15 min

The Security Hole in String Comparison

This authentication check has a vulnerability that could expose your secrets.

View All Challenges →