AWS Lambda & Event-driven Architecture Part-1

---

📌 Introduction to AWS Lambda with Events and Best Practices for Event-Driven Architectures

• This section covers:

  • How AWS Lambda works with events

  • AWS Lambda best practices

  • Event-driven architectures

---

🧠 Understanding AWS Lambda and Event-Driven Architecture

• AWS Lambda is an excellent fit for event-driven architectures due to its event-triggered nature.

• Events that trigger Lambda can originate from many AWS resources.

• AWS Lambda is a compute service that runs custom function code and returns a response to the triggering event.

• Most AWS services generate events for internal communication and serve as event sources for Lambda functions.

• All Lambda executions are handled internally via the Lambda API—no direct invocation is allowed from outside.

• As shown in the image, Lambda interacts with events solely through the Lambda API.

---

🟩 Lambda Invocation and Duration

• A Lambda function is triggered by an event—this is called an invocation.

• Lambda functions are limited to 15 minutes of execution time.

• However, most calls across AWS customers take less than a second.

• Some compute-intensive operations may take several minutes, but this is not the common case.

---

🔗 Examples of Lambda Event Triggers

• Lambda can be triggered by various events, such as:

  • HTTP requests from Amazon API Gateway

  • Scheduled tasks from Amazon EventBridge Rule

  • Amazon S3 notifications (e.g., when an object is uploaded)

• Even the simplest Lambda-based applications use at least one event source.

• That’s why Lambda is a natural fit for event-driven architectures—events are the fuel of Lambda.

---

📄 Events as JSON Objects

• An event is a JSON object containing information about what happened.

• Events:

  • Represent a change in system state

  • Are immutable

• An example event JSON is shown in the image.

---

🔍 Using the Event Object in Lambda Handler

• The Lambda handler method always takes the event JSON object as its first parameter.

• Developers can access event details using this object inside the handler.

• Example:

    event.source
    event.detail
  

• In the slide image example, a "New Order" event triggers a Lambda function.

  • You can extract the value using event.detail.

  • You can also access event.source.

---

🔁 Types of Events Triggering Lambda

• Events can be:

  • Custom-generated by other microservices (e.g., “New Order” event in an ecommerce app)

  • Generated by AWS services, such as:

    • Amazon SQS: When a new queue message is available, it triggers Lambda by polling the queue.

---

🧱 Principles of Event-Driven Architecture with Lambda

• Event-driven architectures rely on:

  • Creating events for all application state changes

  • These events are observable by other services.

• The event publisher system is unaware of which consumers subscribe to the event.

• This creates loosely coupled services.

• Most Lambda-based applications use a combination of AWS services depending on needs for:

  • Storage

  • API management

  • Integration with other systems/services

---

🧠 Lambda’s Role in Microservice-Based Architectures

• Lambda acts as the connector between services, applying business logic and transforming data between microservices.

• Serverless applications typically:

  • Use several AWS services

  • Integrate these with custom Lambda function code

  • Communicate via events

---

🔌 Common AWS Services Integrated with Lambda

• As shown in the slide image, the most commonly used AWS services in serverless applications with Lambda include:

  • Compute:

    • AWS Lambda

  • Data Storage:

    • Amazon S3

    • DynamoDB

    • Amazon RDS

  • API Management:

    • Amazon API Gateway

  • Integration:

    • Amazon SNS

    • Amazon SQS

    • Amazon EventBridge

  • Orchestration:

    • AWS Step Functions