Lambda

⚙️ What is AWS Lambda?

AWS Lambda is a serverless compute service that lets you run code without provisioning or managing servers. You only pay when your code runs.

Lambda scales automatically and runs your function in response to events like API calls, file uploads, or database changes.

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🔧 Key Concepts

Concept	Description
Function	Your code + configuration (runtime, memory, timeout, etc.)
Trigger	Event source that invokes the function (e.g., S3, API Gateway, DynamoDB)
Runtime	Programming language supported (Node.js, Python, Go, Java, .NET, etc.)
Execution Role	IAM role that grants your function permission to use other AWS services
Handler	Entry point of your function (e.g., index.handler)

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🚀 Common Use Cases

Category	Example
🧩 Microservices	Run REST API endpoints via API Gateway
📁 File Processing	Process S3 uploads (e.g., resize images, extract metadata)
🔄 Automation	Periodic tasks via EventBridge (e.g., clean up, reports)
🔗 Event-driven apps	React to DynamoDB, Kinesis, SNS, or SQS changes
🔒 Security	Real-time security checks, IAM automation

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🛠️ Supported Runtimes

• Python (python3.11, 3.9, 3.8)

• Node.js (nodejs20.x, 18.x, 16.x)

• Go (provided.al2023)

• Java, .NET, Ruby, and custom runtimes via container images

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🧪 Event Sources (Triggers)

Source	Event
S3	PUT, POST, DELETE objects
API Gateway	HTTP/REST requests
DynamoDB	Insert/modify/delete items
EventBridge	Scheduled (cron) or event bus
SQS	Messages in queue
CloudWatch	Logs, metrics, alarms
Cognito	User pool auth triggers

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🧱 Lambda Function Structure (Python)

# index.py
def handler(event, context):
    print("Received event:", event)
    return {
        "statusCode": 200,
        "body": "Hello from Lambda!"
    }

Handler format: file_name.function_name (e.g., index.handler)

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📦 Terraform Example – Deploy Basic Lambda Function

resource "aws_iam_role" "lambda_exec" {
  name = "lambda_exec_role"

  assume_role_policy = jsonencode({
    Version = "2012-10-17",
    Statement = [{
      Action = "sts:AssumeRole",
      Effect = "Allow",
      Principal = {
        Service = "lambda.amazonaws.com"
      }
    }]
  })
}

resource "aws_iam_role_policy_attachment" "lambda_policy" {
  role       = aws_iam_role.lambda_exec.name
  policy_arn = "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
}

resource "aws_lambda_function" "my_lambda" {
  function_name = "yuva-lambda-demo"
  role          = aws_iam_role.lambda_exec.arn
  handler       = "index.handler"
  runtime       = "python3.11"
  filename      = "lambda.zip"  # Zip file containing index.py

  source_code_hash = filebase64sha256("lambda.zip")
}

📁 Create lambda.zip:

zip lambda.zip index.py

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🧑‍💼 Lambda IAM Permissions

Attach policies to allow Lambda to access:

AWS Service	Required IAM Actions
S3	s3:GetObject, s3:PutObject
DynamoDB	dynamodb:GetItem, dynamodb:PutItem
SNS/SQS	sns:Publish, sqs:SendMessage
CloudWatch	logs:*

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📊 Monitoring & Logs

• Amazon CloudWatch is used to:

  • View Lambda logs

  • Set alarms based on errors, duration, invocations

• Use AWS X-Ray for tracing

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📈 Pricing

Metric	Value
Free Tier	1 million requests/month, 400,000 GB-seconds
Invocations	$0.20 per 1 million requests
Duration (GB-sec)	$0.00001667 per GB-second

Example: 128 MB Lambda running for 1 sec = 0.0000021 USD

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🔐 Security Tips

• ✅ Use least privilege IAM role

• ✅ Enable VPC if accessing RDS or private resources

• ✅ Set a timeout (default: 3s, max: 15 min)

• ✅ Use environment variable encryption (KMS)

• ✅ Use layers to share code (e.g., boto3, numpy)

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🧰 Advanced Features

Feature	Description
Lambda Layers	Share libraries (e.g., requests, pandas) across functions
Concurrency	Set max parallel executions (throttle)
Versions/Aliases	Use for deployments, staging, traffic shifting
Function URLs	Built-in HTTPS endpoint (no API Gateway)
Container Image	Package large apps as Docker images (max 10 GB)

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✅ TL;DR Summary

Feature	AWS Lambda
What is it?	Serverless compute for event-driven workloads
Languages	Python, Node.js, Go, Java, etc.
Trigger Sources	S3, API Gateway, EventBridge, DynamoDB, etc.
Max Timeout	15 minutes
Max Memory	10 GB
Package Types	ZIP (50MB) or Docker (10 GB)
Terraform Support	✅ Yes (aws_lambda_function)

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