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Introduction

App crashes during traffic spike 💀🥺
Monitoring ensures uptime & speed
Logging tracks errors & actions
👺 Myth : “I’ll check manually”
Example: Slow “lifestyle” filter

Imagine your blogging app hosts a viral post. Thousands of users flood in, and the app crashes. Without monitoring, you don’t know why, and without logs, you can’t fix it quickly. This lecture shows why these tools are critical for keeping your app reliable.

Monitoring tracks metrics like uptime and response times, acting like a dashboard to ensure your app is always available and fast for users browsing or filtering posts.

Logs record every event, like a user filtering posts by “tech” or an admin saving a draft, giving you a detailed history to debug issues or analyse user behaviour.

Many students think manual checks are enough, but with complex features like tag-based filtering or admin panels, only automated monitoring and logging can keep up with issues.

In our blogging app, monitoring shows a query for “lifestyle” posts take 5 seconds, and logs reveal it’s scanning too many records, guiding you to optimise the database for better performance.

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Use Cases

Uptime : Keep app online ( UptimeRobot )
Performance : Ensure speed ( New Relic )
Debugging : Fix errors fast ( Sentry , Winston )
Security : Detect threats

Let's explore which are the primary use cases for monitoring and logging.

You should always make sure that your application is online. Monitoring tools like UptimeRobot check if your blogging app is reachable every minute, alerting you instantly if it goes down to ensure users can always access posts.

You also should know if and when your application struggles with performance. Tools like New Relic track response times and catch slow endpoints like filtering posts by tag, so you can optimise for a smooth user experience.

It is also impertinent when debugging your applications. Logs in tools like Sentry or Winston show why a post failed to save, like a missing title, allowing you to add validation and resolve issues quickly in the admin panel.

Considering the security of your apps, you can use logs to detect threats. Logs reveal suspicious activity, like repeated failed logins, and monitoring alerts you to block potential attacks on the admin panel, keeping your app secure.

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Example

    import express from 'express';
import winston from 'winston';
import { Request, Response } from 'express';

const app = express();
const logger = winston.createLogger({
  level: 'info',
  format: winston.format.combine(
    winston.format.timestamp(),
    winston.format.json()
  ),
  transports: [
    new winston.transports.File({ filename: 'app.log' }),
    new winston.transports.Console()
  ]
});

app.use(express.json());

app.get('/posts', (req: Request, res: Response) => {
  const { tag } = req.query;
  logger.info('User filtered posts', { tag, timestamp: new Date() });
  // Simulate fetching posts
  res.json([{ id: 1, title: 'Sample Post', tag }]);
});

app.post('/admin/posts', (req: Request, res: Response) => {
  const { title } = req.body;
  if (!title) {
    logger.error(
      'Post save failed', 
      { error: 'Missing title', timestamp: new Date() });
    return res.status(400).json({ error: 'Title is required' });
  }
  logger.info('Post saved', { title, timestamp: new Date() });
  res.json({ message: 'Post saved' });
});

app.listen(3000, () => {
  logger.info('Server started on port 3000');
});

Let's check out an example. This code sets up logging for our blogging app using Winston. It logs user actions like filtering posts by tag and admin actions like saving posts, helping us track behaviour and debug errors, which are key use cases for logging.[

This is an expressJS application that uses Winston library to create logs.

We configure Winston to log in JSON format with timestamps.

The logs are save to file and to console.

This is an example of how to use the logger. It logs when a user filters posts by tag, capturing the tag and timestamp, which helps analyse popular filters like “tech” or “lifestyle” in our blogging app.

This line logs failed post saves in the admin panel, recording errors like missing titles to aid debugging, a critical use case for maintaining the admin panel.

This line logs when the post saves successfully. That's it, simple and effective. you can configure Winston to save logs in a database or post them to an external service. Just make sure logging is not slowing down your app. It's best to keep it asynchronous.

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Stress Testing

Stress test : Simulate heavy traffic
Find bottlenecks : Optimize weak points
Example : 10,000 users filtering
Tools : Locust , JMeter , k6

Apart from monitoring and logging it is also important to know the limits of your app.

So, stress testing tools like Locust mimic thousands of users filtering posts to see if your blogging app can handle a traffic spike, ensuring uptime under pressure.

Tests reveal issues like slow database queries, allowing you to add indexes or caching to improve performance for users and admins.

For example, testing 10,000 users filtering by “lifestyle” shows a slow query. Logs and monitoring guide you to optimise it, ensuring the app stays reliable. In this case, caching fixes it, and the app handles 100,000 users and more!

Many tools can help. Locust simulates user traffic, JMeter tests specific endpoints like posts, and K6 offers modern scripting for stress testing your blogging app. You have many options and we hope you'll use them!

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Key Takeways

Monitor uptime, speed, errors
Log all events, not just errors
Stress test for traffic spikes
Pitfall: Don’t skip automation

Full Stack Development

Monitoring and Logging

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Introduction

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Use Cases

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Example

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Stress Testing

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Key Takeways