A high-performance notification engine built with Java 21, designed to handle massive concurrency using Virtual Threads and ensuring "at-least-once" delivery with robust resilience patterns.
- Java 21 Virtual Threads: Massive throughput with minimal memory footprint by leveraging Project Loom.
- Redis Idempotency: Prevents duplicate notifications using a fail-open SETNX strategy.
- Resilience4j Retries: Exponential backoff for flaky downstream SMS/Email providers.
- Dead Letter Queue (DLQ): Automatic persistence of failed notifications to H2/JPA for manual recovery.
- Strategy Pattern: Easily extensible architecture for adding new channels (Email, SMS, Push, etc.).
Framework: Spring Boot 3.4+
- Runtime: Java 21 (Temurin)
- Database: H2 (DLQ Storage)
- Cache: Redis (Idempotency)
- Documentation: SpringDoc OpenAPI (Swagger)
Prerequisites
- JDK 21
- Maven 3.9+
- Redis (Local or Cloud)
Header: Idempotency-Key: <unique-uuid>
JSON
{
"userId": "user_123",
"channel": "EMAIL",
"templateId": "welcome_email",
"payload": {
"name": "John Doe"
}
}
Automated pipeline via GitHub Actions:
- Build: Compiles on JDK 21.
- Test: Runs integration tests with Redis/DB mocks.
- Deploy: Pushes Docker image to GitHub Container Registry (GHCR).
MIT