Tired of Missing Lambda Errors? Set Up CloudWatch Alarms with SNS Alerts.

Introduction.

Monitoring serverless applications effectively is crucial in modern cloud-native architectures. AWS Lambda, a cornerstone of serverless computing, allows developers to build scalable and cost-efficient applications without managing servers. However, even the most well-designed Lambda function can fail due to code bugs, misconfigurations, or unexpected input. When Lambda invocation errors occur, it’s vital to detect them as quickly as possible to minimize downtime and ensure a seamless user experience.

That’s where Amazon CloudWatch and Amazon SNS (Simple Notification Service) come into play. CloudWatch is AWS’s monitoring and observability service that provides actionable insights into your applications and infrastructure. With CloudWatch, you can track metrics like invocation counts, execution durations, and errors. One of its most powerful features is the ability to create alarms based on these metrics, allowing for automated responses and alerts.

On the other hand, Amazon SNS is a fully managed pub/sub messaging service designed to send notifications from the cloud to end-users or other applications. When used in conjunction with CloudWatch, SNS can immediately notify your team whenever a CloudWatch alarm is triggered—via email, SMS, or even Lambda-to-Lambda communication—so issues can be addressed before they escalate.

This blog post will walk you through a real-world scenario: setting up a CloudWatch alarm that monitors AWS Lambda invocation errors and automatically sends a notification through SNS when something goes wrong. Whether you’re building a small application or managing a large-scale distributed system, this approach ensures that you’re not left in the dark when functions start failing.

We’ll begin by explaining the concepts behind CloudWatch metrics, particularly the “Errors” metric that reflects invocation failures. Then, we’ll dive into creating an SNS topic, subscribing to that topic (so you or your team receive alerts), and finally, configuring a CloudWatch alarm that ties everything together. By the end of this tutorial, you’ll have a fully functional monitoring system that proactively notifies you of Lambda issues.

Even if you’re new to AWS or serverless, don’t worry—this guide breaks each step down into manageable instructions, with clear explanations and tips for best practices. If you’re already experienced with AWS services, you may find some optimization tips and automation ideas helpful to further streamline your monitoring setup.

Beyond just detecting failures, setting up alarms is part of a larger DevOps mindset: promoting observability, reducing Mean Time to Recovery (MTTR), and building confidence in your deployments. It empowers developers and operations teams to respond swiftly and intelligently to issues, and ultimately contributes to higher application reliability.

You’ll also learn about alarm tuning—so you’re not overwhelmed by false positives—and gain a deeper understanding of how CloudWatch and SNS integrate with other AWS services like Lambda, EventBridge, and more. This knowledge will help you design smarter alerting systems as your cloud environment grows.

Whether you’re preparing for production readiness, hardening your alerting strategy, or simply learning how AWS services work together, this tutorial is for you. Let’s get started and ensure your Lambda functions are monitored effectively, with real-time error detection and instant notifications when things go wrong.

Prerequisites

• An AWS Lambda function already deployed.
• IAM permissions to access CloudWatch, Lambda, and SNS.
• AWS CLI or access to the AWS Management Console.

Step-by-Step Instructions

Step 1: Create an SNS Topic

1. Go to the SNS console: https://console.aws.amazon.com/sns/
2. Click “Create topic”.
3. Choose Standard type.
4. Name your topic (e.g., LambdaErrorNotifications).
5. Click “Create topic”.

Step 2: Subscribe to the SNS Topic

1. On the SNS topic page, click “Create subscription”.
2. Protocol: Select Email (or other protocol).
3. Endpoint: Enter your email address.
4. Click “Create subscription”.
5. Check your email and confirm the subscription.

Step 3: Open CloudWatch Console

• Go to: https://console.aws.amazon.com/cloudwatch/

Step 4: Create a CloudWatch Alarm for Lambda Errors

1. In the left menu, go to “Alarms” > Click “Create alarm”.
2. Select metric:
   • Choose Browse > Lambda > By Function Name.
   • Select your Lambda function.
   • Choose the metric: Errors (under Invocations).
3. Click “Select metric”.
4. Configure the metric:
   • Period: e.g., 1 minute or 5 minutes.
   • Statistic: Sum.
   • Threshold type: Static.
   • Whenever Sum is…: Greater than 0.
5. Click “Next”.

Step 5: Configure the Alarm Action

1. In Alarm state trigger: Select In alarm.
2. Send a notification to: Choose your SNS topic (LambdaErrorNotifications).
3. Click Next.

Step 6: Name and Create the Alarm

1. Name: Give your alarm a name (e.g., Lambda-Error-Alarm).
2. (Optional) Add a description.
3. Review your settings.
4. Click “Create alarm”.

Done! You’ve set up:

• A CloudWatch alarm for Lambda invocation errors.
• An SNS topic that sends notifications when the alarm is triggered.

Conclusion.

In today’s fast-moving cloud environments, proactive monitoring is not just a best practice—it’s essential. AWS Lambda offers powerful, serverless compute capabilities, but even the best code can encounter unexpected errors. By configuring a CloudWatch alarm to monitor Lambda invocation errors and integrating it with SNS for real-time notifications, you’re adding a critical layer of observability to your application architecture.

This setup ensures that you or your team are immediately alerted the moment something goes wrong, allowing for faster investigation, quicker remediation, and reduced impact on end users. It also lays the groundwork for automation, self-healing systems, and better incident response workflows.

Beyond the specific use case of Lambda errors, this same monitoring pattern can be applied across many AWS services—whether you’re tracking EC2 CPU utilization, RDS latency, or API Gateway throttling. CloudWatch and SNS together form a versatile, scalable, and cost-effective solution for staying on top of your infrastructure and application health.

If you haven’t already, consider extending this setup with tools like AWS Lambda Destinations, CloudWatch Logs Insights, or integrating alerts with third-party platforms like Slack or PagerDuty for even better visibility and response times.

By taking the time to configure alarms and notifications today, you’re investing in the long-term reliability, resilience, and performance of your cloud-based applications. Monitoring isn’t just about catching errors—it’s about building confidence in your systems. Stay alert, stay informed, and stay ahead.