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Amazon EventBridge is AWS’s powerful event bus that lets you automate tasks, connect services, and react to events in real-time—without servers. Arjun, a new cloud engineer, discovered its power while preparing for the AWS Solutions Architect exam.
Arjun, a freshly minted cloud engineer, was deep into AWS training. His goal? Pass the AWS Certified Solutions Architect – Associate exam and become a master of building smart, event-driven architectures.
But Arjun had a problem.
He needed to:
- Run a Lambda every night at 2 AM.
- Get notified when the root account was used (huge security risk).
- Automatically react when a build failed in AWS CodeBuild.
- Trigger EC2 actions when specific events happened.
At first, he thought of writing custom scripts and setting up crons on an EC2 instance. But it felt… old-school. 🤨
That’s when he stumbled upon Amazon EventBridge.
🧠 What Is Amazon EventBridge?
Imagine if all your AWS services could talk to each other and react to events in real-time—without you writing a bunch of glue code.
That’s EventBridge a smart middleman that listens to everything happening in AWS—and when something important happens, it instantly takes action.
EventBridge allows services (like EC2, S3, CodeBuild, etc.), third-party apps (like Datadog, Zendesk), or even your own apps to send events, and take actions in response—like triggering a Lambda, sending an SNS alert, or starting an ECS task.
It is a managed, pay-as-you-go service that lets your apps and AWS services talk through events—with zero infrastructure headaches.
You can:
- Run a function when a file is uploaded
- Get notified when root user logs in
- Schedule tasks (like a cron job)
- Trigger workflows when a build fails
And you do all of this without setting up servers. Just connect the dots.
🔁 Arjun’s First Use-Case: Scheduled Lambda
Arjun needed to run a script every day at 2 AM. Normally, he’d think cron.
But with EventBridge, he simply created a rule like this:
And that rule triggered his Lambda, without needing a server or worrying about uptime. 🔥
He smiled. “Okay, this is cool.”
🚨 Root User Sign-In Alert? Handled!
Security was always on Arjun’s mind.
He created a rule in EventBridge to listen for the RootLogin event from CloudTrail.
When that happened, EventBridge fired a message to SNS, which sent Arjun an email:
📬 “ALERT: Someone used the root account!”
No cron. No polling. Just pure reaction.
🛠️ How Amazon EventBridge Works
🧃 1. Amazon EventBridge Event Sources – “Who’s Speaking?”
In Amazon EventBridge, every action in AWS or your applications is called an event. Think of each AWS service as a character in a movie—performing actions that might matter to your workflow.
Common Event Sources in Amazon EventBridge include:
- EC2 → Starts, stops, or terminates instances
- S3 → Uploads, deletions, or object modifications
- CloudTrail → Logs API calls and account activity
- Third-Party Apps → External services like Auth0, Zendesk, Shopify, and others can also send events
These actions are called events.
So the event source is the origin of that action.
They shout:
“Hey! Something happened!” 👋
And Arjun, being the wise engineer, wants to listen to those important events only.
🚍 2. Amazon EventBridge Event Bus – “The Messenger That Delivers Events”
The Event Bus is like a delivery van that carries these events to whoever is interested.
There are 3 types of buses:
🟢 Default Event Bus
- Handles all events from AWS services
- Automatically set up
- Example: EC2 stops → Event sent to the default event bus
🟣 Partner Event Bus
- For 3rd-party SaaS tools (like Auth0, Datadog)
- They can publish events directly to your AWS account
🟡 Custom Event Bus
- For your own applications
- You can write custom events like
orderPlaced,userDeletedetc., and send them to a custom bus
So think of each Event Bus as a channel of communication, depending on who is talking.
🔎 3. Amazon EventBridge Rules – “What Are You Interested In?”
Now Arjun doesn’t want to listen to every event. That’s noisy.
So he sets up rules, like:
“Only tell me when an EC2 instance is terminated”
“Only when the root user signs in”
“Only when an object is added toproduction-bucket“
A rule is like a filter.
It looks at the event and says:
- “Do I care?”
- ❌ No → ignore.
- ✅ Yes → pass it to the target.
🎯 4. Amazon EventBridge Targets – “What Should Happen Now?”
This is the fun part.
Once a rule matches, it can trigger an action. These are called targets.
Here’s what Arjun can choose to do:
- 🚀 Lambda Function – Run code instantly
- 📨 SNS Topic – Notify a team via email, SMS
- 📬 SQS Queue – Push into a message queue for another service
- ⚙️ SSM Automation – Trigger automated tasks (like patching)
- 🛠️ CodeBuild – Start building and deploying code
- 📦 ECS Task – Run a container
- 🧭 Step Function – Kick off a multi-step workflow
And it’s all serverless – Arjun doesn’t set up any infrastructure. AWS handles everything behind the scenes.
📈 Amazon EventBridge Scales Like Magic (Serverless)
There are no servers to manage.
No EC2. No autoscaling groups. Nothing.
- It handles 100 events or 1 million the same way
- No maintenance
- Pay only per event processed
That’s why it’s called a serverless event bus — it’s like a central nervous system that just works.
🔁 Event Replay & Archive with Amazon EventBridge
One day, Arjun’s app broke because of a bug in his Lambda function. Arjun was smart — he had enabled event archiving in EventBridge.
What does that mean?
- EventBridge stores every event it receives
- Like a digital notebook that remembers every action — in JSON format
- This is helpful when something goes wrong, and you want a second chance
After fixing the bug, he used Replay to resend the same old event — just like hitting a rewind button.
✅ Problem solved.
❌ No lost data.
Even in hundreds or thousands of events, you can filter the one you want to replay based on:
- Event time
- Event type (e.g. only S3 upload events)
- Specific resources (like a certain S3 bucket)
🧩 Schema Registry — Organize Event Data with Amazon EventBridge
Arjun was getting lots of events — like S3 uploads, EC2 actions, and more.
But each event was like a different-shaped puzzle piece — confusing to work with!
That’s where Schema Registry comes in:
- It watches the events that go through EventBridge
- It figures out their structure (what fields they have, like
bucketName,timestamp, etc.) - It gives Arjun a ready-made guide (called a “schema”) showing what the data looks like
Even better — Arjun can download code templates that already understand this data.
So instead of guessing or checking JSON files manually, Arjun just says:
“Hey AWS, give me the blueprint and the code.”
And boom — he’s coding faster and safer. It saves time, avoids errors, and makes coding with events way easier, especially when there are lots of event types coming in.
🔒 Cross-Account Event Management with Amazon EventBridge
Arjun’s company had many AWS accounts.
Using permissions (resource policies), he allowed other accounts to send their events to one central account.
Now, Arjun had one clear view of everything happening across all teams — all in one place.
No more jumping between accounts!
🧠 Arjun’s Takeaway
“EventBridge lets me build smart reactions to anything happening in my system — whether it’s an AWS service, a 3rd-party app, or my own code — without managing any of the plumbing.”
It’s like turning your AWS account into a fully automated robot brain:
- It listens
- It filters
- It reacts
- It scales
All without servers.
FAQ
Q1: What is Amazon EventBridge?
Amazon EventBridge is a serverless event bus that allows AWS services, third-party apps, and your own applications to communicate via events. It automatically routes events to targets like Lambda, SNS, or Step Functions for real-time responses.
Q2: How does EventBridge differ from CloudWatch Events?
EventBridge is the evolution of CloudWatch Events. It supports more event sources, partner integrations, custom event buses, and schema discovery to simplify event-driven architectures.
Q3: What are Event Sources in EventBridge?
Event Sources are the origin of events. They can be AWS services (like EC2 or S3), third-party apps (like Datadog or Shopify), or custom applications. EventBridge listens to these sources and triggers actions based on rules.
Q4: What are Rules and Targets in EventBridge?
Rules filter events to decide which ones are important. Targets define what happens when a rule matches, like invoking a Lambda, sending an SNS message, or triggering a Step Function workflow.
Q5: Can EventBridge be used for scheduling tasks?
Yes! EventBridge can replace cron jobs by scheduling tasks at specific times or intervals, and trigger Lambdas or other targets without managing servers.
Q6: How does Event Replay & Archive work?
EventBridge can store all received events in an archive. If something goes wrong, you can replay selected events to reprocess them, making debugging and recovery easier.
Q7: Is EventBridge serverless?
Yes! EventBridge scales automatically, requires no servers to manage, and you pay only for events processed.
Q8: Can EventBridge handle cross-account events?
Absolutely. You can configure permissions so multiple AWS accounts send events to a central account for unified monitoring and reaction.
Q9: Do I need to write custom code to use EventBridge?
Minimal code is required. Most tasks, like routing events to Lambda, SNS, or SQS, can be configured using the AWS Console or JSON rules without building infrastructure.
Q10: How is Amazon EventBridge priced?
EventBridge uses a pay-per-use pricing model. You only pay for the number of events published, matched, and delivered, plus optional features like event archiving and replay. There are no upfront costs or servers to manage.
Read More on AWS Monitoring
- Amazon CloudWatch Logs Insights: A Beginner’s Guide
- Difference between AWS CloudWatch, CloudTrail and Config
- Understanding AWS EventBridge: The Automation Service Explained
- Understanding AWS CloudWatch Alarms: Listen to Your Cloud Signals
- How CloudWatch Agent Completes EC2 Monitoring: A Comprehensive Guide
- Understanding Live Tail in Amazon CloudWatch Logs
- Master AWS Resource Monitoring with CloudWatch Metrics
- An Introduction to CloudWatch Logs: What You Need to Know
- Understanding Amazon CloudWatch: A Comprehensive Guide
Your writing has a way of resonating with me on a deep level. I appreciate the honesty and authenticity you bring to every post. Thank you for sharing your journey with us.
Thanks Jayde Blick for your kind words.
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Thank you so much for your kind words! 🙏 I’m really glad you found value in my blog.
Your ability to distill complex concepts into digestible nuggets of wisdom is truly remarkable. I always come away from your blog feeling enlightened and inspired. Keep up the phenomenal work!
That really means a lot — thank you! 🙏 My goal is always to make complex topics easier to understand, so I’m glad to hear it’s helping and inspiring you.