Cloud Watch Events abd EventBridge
CloudWatch Events
A service for monitoring events from AWS services.
Example: “Every day at 9 AM trigger a Lambda” or “When an EC2 instance state changes, trigger something.”
Think of it like a basic scheduler + event notifier.
EventBridge (newer, upgraded version)
EventBridge is basically CloudWatch Events 2.0 (they’re the same service, just evolved).
It does everything CloudWatch Events does, plus:
Accepts events from AWS services, SaaS apps (like Zendesk, Shopify), and custom apps.
Has rules to filter, transform, and route events.
More powerful integrations (Step Functions, Kinesis, etc.)
Analogy
CloudWatch Events: A school bell — it rings at certain times (schedule) or when something happens (event).
EventBridge: A full event manager — not only rings the bell but also routes messages between teachers, students, and even parents’ apps with custom rules.
Flow EventBridge
Event happens → A file is uploaded to S3.
Event sent to EventBridge.
Rule filters → “Only .jpg files.”
Target triggered → Lambda adds a watermark.
Event Bus (in EventBridge)
An event bus is like a channel or pipeline where events are sent and then routed to the right targets.
Event producers put events on the bus (e.g., S3, EC2, custom apps).
Rules on the bus decide which events should go where.
Targets (like Lambda, Step Functions, SNS) receive the event and act on it.
Types of Event Buses
Default Event Bus
Already available in your account.
AWS services automatically send their events here (e.g., S3 file upload, EC2 state change).
Custom Event Bus
You create it for your own apps/events.
Example: Your app publishes an event “NewOrderPlaced,” and you route it to a payment Lambda.
Partner Event Bus
For SaaS apps integrated with AWS (like Zendesk, Shopify, or Datadog).
Events from these apps go through this bus.
Analogy
Think of an event bus like a city bus 🚍:
People (events) get on the bus.
The bus (event bus) carries them.
They get off at the correct stops (targets) based on rules.
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