Health check endpoints in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a basic health check endpoint using Express.

Node.js

const express = require('express');
const app = express();

app.get('/health', (req, res) => {
  res.status([1]).send('OK');
});

app.listen(3000);

Drag options to blanks, or click blank then click option'

A404

B200

C500

D302

Attempts:

3 left

💡 Hint

Common Mistakes

Using 404 or 500 status codes which indicate errors.

Forgetting to send a response.

The health check endpoint should respond with HTTP status 200 to indicate the service is healthy.

2fill in blank

medium

Complete the code to send a JSON response with status and uptime in the health check endpoint.

Node.js

app.get('/health', (req, res) => {
  res.status(200).json({
    status: 'ok',
    uptime: process.[1]()
  });
});

Drag options to blanks, or click blank then click option'

Auptime

BmemoryUsage

CcpuUsage

Denv

Attempts:

3 left

💡 Hint

Common Mistakes

Using memoryUsage or cpuUsage which return different info.

Trying to access a property instead of calling a method.

The process.uptime() method returns the number of seconds the current Node.js process has been running, useful for health checks.

3fill in blank

hard

Fix the error in the health check middleware to properly handle asynchronous checks.

Node.js

app.get('/health', async (req, res) => {
  const dbHealthy = await checkDatabaseConnection();
  if (!dbHealthy) {
    res.status([1]).json({ status: 'error' });
  } else {
    res.status(200).json({ status: 'ok' });
  }
});

Drag options to blanks, or click blank then click option'

A200

B500

C404

D503

Attempts:

3 left

💡 Hint

Common Mistakes

Using 200 status code even when the database is down.

Using 404 which means not found.

When a dependent service like a database is down, the health check should respond with HTTP 503 Service Unavailable.

4fill in blank

hard

Fill both blanks to create a reusable health check middleware that sends JSON status and sets correct HTTP status code.

Node.js

function healthCheckMiddleware(req, res) {
  const healthy = checkSystemHealth();
  res.status([1]).json({ status: [2] });
}

Drag options to blanks, or click blank then click option'

A200

B'ok'

D503

Attempts:

3 left

💡 Hint

Common Mistakes

Using numeric status code as string or vice versa.

Sending status code 503 when system is healthy.

The middleware should respond with status 200 and JSON status 'ok' when the system is healthy.

5fill in blank

hard

Fill all three blanks to create an advanced health check endpoint that checks database, cache, and returns appropriate status.

Node.js

app.get('/health', async (req, res) => {
  const dbOk = await checkDB();
  const cacheOk = await checkCache();
  if (dbOk && cacheOk) {
    res.status([1]).json({ status: [2] });
  } else {
    res.status([3]).json({ status: 'error' });
  }
});

Drag options to blanks, or click blank then click option'

A200

B'ok'

C503

D'healthy'

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong status codes for failure.

Returning wrong status string for success.

When both database and cache are healthy, respond with 200 and status 'ok'. Otherwise, respond with 503 and status 'error'.