Event Notification Service - AWS

Serverless event-driven system on AWS

A serverless event notification system built on AWS that enables publishers to submit events and subscribers to receive notifications through email or webhooks based on filtering preferences. Wanted to learn cloud architecture and serverless patterns.

Features:

  • Event ingestion via REST API with API key authentication
  • Multi-channel delivery (email via SES, webhooks via HTTP)
  • Asynchronous processing with SQS buffering
  • Dead-letter queue for failed messages
  • CloudWatch monitoring and alerting


Tech Stack

  • Cloud Platform: AWS
  • Compute: Lambda (3 serverless functions)
  • API: API Gateway with API key auth
  • Messaging: SQS (main queue + DLQ)
  • Database: DynamoDB (Events, Subscriptions, Notifications)
  • Notifications: SES (email), SNS (alerts)
  • Monitoring: CloudWatch Logs & Alarms
  • Security: IAM least-privilege policies


Architecture

Event-driven serverless architecture with decoupled components:

Publisher
    │
    │ POST /events
    ▼
┌─────────────┐    ┌─────────────┐    ┌─────────────────────┐
│ API Gateway │──> │   Lambda    │───>│        SQS          │
└─────────────┘    │  (Ingest)   │    │   (events-queue)    │
                   └─────────────┘    └──────────┬──────────┘
                                                 │
                                                 ▼
            ┌──────────────────┐       ┌─────────────────────┐
            │     DynamoDB     │<──────│      Lambda         │
            │    (Events &     │       │    (Processor)      │
            │  Notifications)  │       │                     │
            └──────────────────┘       └─────────┬───────────┘
                                                 │
                                          ┌──────┴──────┐
                                          ▼             ▼
                                      ┌───────┐    ┌─────────┐
                                      │  SES  │    │ Webhook │
                                      │(Email)│    │  (HTTP) │
                                      └───────┘    └─────────┘

        ┌────────────┐     ┌──────────────┐
        │    DLQ     │────>│  CloudWatch  │────> Alert Email
        │ (failures) │     │    Alarm     │
        └────────────┘     └──────────────┘


Key Features & Implementation

  1. Event Ingestion - REST API via API Gateway accepts events with type, severity, and metadata, triggering Lambda for validation and SQS submission.
  2. Subscription Management - DynamoDB stores subscriber preferences with filters for event type and severity levels.
  3. Asynchronous Processing - SQS buffers events for reliable async processing with Lambda polling for fault tolerance.
  4. Multi-Channel Delivery - Event processor Lambda matches subscriptions and sends notifications via SES (email) or HTTP webhooks.
  5. Error Handling & Monitoring - Dead-letter queue captures failed messages, CloudWatch alarms trigger SNS alerts for system health monitoring.


API Endpoints

POST /events - Submit new event

{
  "eventType": "deployment",
  "severity": "HIGH",
  "title": "API v2.1 deployed to production",
  "details": {
    "service": "user-api",
    "version": "2.1.0"
  }
}

POST /subscriptions - Create notification subscription

{
  "eventType": "deployment",
  "severityFilter": "HIGH",
  "channel": "EMAIL",
  "target": "ops-team@company.com"
}


Learnings

  1. New Technologies: AWS Lambda, API Gateway, SQS, DynamoDB, SES
  2. Use CloudWatch for observability, logging, and alarms; these are critical for debugging and monitoring serverless systems.


Technologies: AWS · Lambda · API Gateway · SQS · DynamoDB · SES · CloudWatch · IAM · Serverless · Event-Driven Architecture