🧠 Understanding the Serverless Architecture
The architecture is fully event-driven:
User uploads an image to the source S3 bucket
S3 emits an ObjectCreated event
AWS Lambda is triggered automatically
Lambda processes the image using Python (Pillow)
Output images are saved to a destination S3 bucket
Execution logs are written to CloudWatch Logs
No servers. No scaling logic. No manual intervention.
🏗 AWS Resources Created with Terraform
Terraform provisions and manages:
_S3 Source Bucket
Versioning enabled
Encryption enabled
Private access
**
S3 Destination Bucket**
Stores processed images
IAM Role for Lambda
Least-privilege access to S3
CloudWatch logging permissions
Lambda Function
Python runtime
Environment variables
Lambda Layer
Contains Pillow dependency
S3 Event Notification
Triggers Lambda on file upload
**
CloudWatch Log Group_**
All resources are fully automated and reproducible
🔐 IAM & Security (Least Privilege)
The Lambda execution role is tightly scoped:
s3:GetObject on source bucket
s3:PutObject on destination bucket
logs:CreateLogGroup
logs:CreateLogStream
logs:PutLogEvents
This ensures:
No unnecessary permissions
Reduced blast radius
Production-grade security posture
🐳 Fixing Dependency Issues with Docker
To solve compatibility problems:
Dependencies are built inside a Docker container
Docker image matches AWS Lambda runtime
Pillow is compiled correctly for Lambda
Layer is zipped and deployed via Terraform
This ensures:
✔ Runtime compatibility
✔ Predictable builds
✔ No import errors
This step reflects real-world serverless best practice.
⚙️ Deployment Automation
Deployment is automated using shell scripts:
Build Lambda layer
Package dependencies
Initialize Terraform
Run terraform plan and terraform apply
This removes:
Manual repetition
Environment inconsistencies
Human error
🧪 Testing the Pipeline
Testing flow:
Upload an image to the source S3 bucket
Lambda is triggered automatically
Image is processed
Multiple output variants appear in destination bucket
Execution details are visible in CloudWatch logs:
Execution time
Memory usage
Billing duration
This validates the entire event-driven pipeline.
🏁 Conclusion
Day 18 demonstrates how Terraform and serverless computing work together to build scalable, cost-efficient, and production-ready systems.
By combining:
Event-driven design
Infrastructure as code
Secure IAM practices
Docker-based dependency management
this project shows real-world serverless automation done correctly.
This is not a demo — this is how modern cloud systems are built and operated.
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