Monitoring Performance with CloudWatch

Once your web application is up and running on AWS, the next question becomes: how do you know it’s working as expected? What happens if user traffic suddenly spikes, or your server begins to slow down? These kinds of questions are where Amazon CloudWatch becomes essential. It’s one of the core tools AWS provides to help you observe, measure, and respond to what’s happening inside your infrastructure.

In this section, we won’t walk through the step-by-step setup process. Since your initial usage of AWS services may still be limited to a single EC2 instance or a small-scale practice app, the monitoring needs are likely minimal for now. But it’s important to understand the key capabilities CloudWatch offers—even if you’re not using them all immediately. Knowing what’s available will help you make better decisions as your project grows.

What can CloudWatch do?

At a glance, CloudWatch is a monitoring tool. But it’s more accurate to think of it as a collection of tools, all working together to give you visibility into your system. It doesn’t just show you charts—it helps you understand what’s happening, detect unusual patterns, and respond automatically when something goes wrong.

Here are the key features you'll likely use as your application grows.

Collecting and viewing metrics

Every time you launch an EC2 instance, connect an RDS database, or use a Load Balancer, AWS automatically sends performance data to CloudWatch. These are called metrics, and they include things like:

• CPU usage on your EC2 server
  
  
• Network traffic in and out of your instance
  
  
• Latency and request counts from your Load Balancer
  
  

You can view these metrics in real-time or look at historical trends. For example, if your server is responding slowly, CloudWatch helps you see whether CPU usage was unusually high at that time. It’s like checking the pulse of your infrastructure.

You’re not limited to default metrics. CloudWatch also lets you send custom metrics—values from inside your app that reflect how things are going. That might be the number of images processed per minute, the success rate of user logins, or how many background jobs are waiting.

Creating alarms to stay ahead

Looking at charts is helpful, but you don’t want to be staring at a dashboard all day.

You can create alarms that watch for certain conditions—like CPU usage going over 80% or the number of errors increasing beyond normal levels. When a threshold is crossed, CloudWatch can:

• Send an email or text message
  
  
• Trigger an action, like launching a new EC2 instance
  
  
• Notify another service (like Lambda) to begin a recovery process
  
  

Think of alarms as your early warning system. They help you catch problems before your users do.

Building custom dashboards

CloudWatch lets you bring everything together into a dashboard—a custom view that shows exactly what you care about. You can create graphs for:

• How busy your web server is
  
  
• How much traffic is flowing through your network
  
  
• How your database read/write performance is trending
  
  
• How many requests your app is handling per minute
  
  

By setting up a dashboard, you create a single place to check the health of your system at any moment. It’s especially helpful during deployments or when troubleshooting an issue.

Working with logs

Metrics are great for showing you that something is off, but they don’t always explain why. For that, you need logs—the actual messages your app and operating system are writing during normal operation.

CloudWatch gives you a place to collect, store, and search your logs. You can:

• Centralize logs from all your EC2 instances
  
  
• Set up filters to find error messages quickly
  
  
• Create visualizations or alarms based on log content
  
  

Let’s say your app starts returning 500 errors. You can use CloudWatch Logs to find out what was happening right before the errors appeared—whether it was a failed database call, a missing file, or something else.

This is especially useful when your infrastructure grows beyond a single instance. Instead of logging into multiple servers to check what's going on, everything is in one place.

Detecting unusual patterns

Not every issue is caused by a specific threshold being crossed. Sometimes, something just looks different—and that’s a clue that something’s off.

CloudWatch can help here too. It includes a feature called Anomaly Detection, which uses machine learning to figure out what “normal” looks like for a given metric. If your application usually handles 50 requests per second at lunchtime, but suddenly drops to 5, CloudWatch can flag that—even if no fixed limit was crossed.

This kind of monitoring is especially helpful for seasonal traffic patterns or workloads that don’t behave the same way every day.

Analyzing logs with CloudWatch logs insights

When things go wrong, speed matters. CloudWatch includes a built-in tool called Logs Insights, which lets you run fast queries across your logs. It’s designed for debugging—finding patterns, counting how often something occurred, or tracking how long certain actions took.

For example, you might write a query to find all log entries containing the word “Timeout,” group them by hour, and visualize the results. That can help you see when things started going wrong and how widespread the problem was.

Logs Insights is like a magnifying glass for your logs. It makes large volumes of data searchable in seconds.

Automating with events and responses

CloudWatch doesn’t just observe—it can act. Through its integration with EventBridge, CloudWatch can respond to events in your system automatically.

Here are a few examples:

• Restart a failed instance
  
  
• Archive logs to S3 when a certain log group gets too large
  
  
• Trigger a Lambda function when your app logs a critical error
  
  

This level of automation helps you build systems that are resilient and self-healing. You define the rules, and CloudWatch ensures they’re followed.

Bringing it all together

Monitoring isn’t just about reacting to failures. It’s about gaining a clear understanding of how your application behaves and making informed decisions as you grow.

CloudWatch gives you that visibility through:

• Metrics for real-time performance data
  
  
• Alarms that keep you informed
  
  
• Dashboards to summarize what’s happening
  
  
• Logs to investigate the root cause of issues
  
  
• Insights and automation to go from data to action
  
  

For the image sharing app we deployed earlier, CloudWatch can help you track server performance, monitor usage patterns, respond to spikes, and understand when things go wrong. Whether your app is serving 10 users or 10,000, CloudWatch scales with you.