Notifly

Notifly: Building a Production-Ready Notification System

Every application needs notifications, but most developers end up with a tangled mess of email libraries and SMS APIs scattered throughout their codebase. I wanted to build something that handles notifications the way they should be handled: as a first-class, reliable, scalable service.

Notifly is a microservice architecture that treats notifications as critical infrastructure, not an afterthought.

The Problem: Notifications Are Harder Than They Look

Building reliable notifications means solving several problems simultaneously:

• Multiple Channels: Email, SMS, push notifications, webhooks - each with different providers and APIs
• Reliability: Messages must be delivered even when services restart or networks fail
• Authentication: Secure token-based auth that works across multiple services
• Observability: You need to know when messages fail and why
• Performance: High throughput without blocking your main application

Most teams hack together a solution that works for their current needs, but breaks down when requirements grow. Notifly is designed to scale from day one.

Architecture: Event-Driven Microservices Done Right

Notifly uses a clean microservice architecture with proper separation of concerns:

User Service: Handles authentication and user management. Built with gRPC for fast internal communication and uses PASETO tokens for stateless, secure authentication.

Trigger Service:
The entry point for notification requests. Validates auth tokens, publishes events to NATS JetStream, and provides the external API interface.

Notification Service: The workhorse that consumes events and actually sends notifications. Implements robust retry logic, provider fallbacks, and detailed error handling.

GraphQL Gateway: Provides a clean, typed API for client applications. Handles authentication and proxies requests to the appropriate services.

Technical Deep Dive: Message Queue Architecture

The heart of Notifly is its message queue implementation using NATS JetStream:

Why NATS JetStream:

• Persistent Storage: Messages survive service restarts
• At-Least-Once Delivery: Guarantees that notifications won't be lost
• Pull-Based Consumers: Services control their own consumption rate
• Built-in Retry Logic: Configurable delivery attempts and backoff

Queue Design: The notification service uses durable consumers with explicit acknowledgment patterns:

goCopy
// Ack: Message processed successfully
msg.Ack()

// Nak: Temporary failure, retry later  
msg.Nak()

// Term: Permanent failure, don't retry
msg.Term()

This gives fine-grained control over retry behavior based on the type of failure.

Production-Ready Features

Security First:

• PASETO tokens for tamper-proof authentication
• gRPC interceptors for authorization
• Parameterized queries prevent SQL injection
• No sensitive data in logs

Observability:

• Structured logging with Zap
• Detailed error reporting with context
• Message delivery tracking
• Performance metrics ready for Prometheus integration

Deployment:

• Docker Compose for local development
• Single binary deployment for production
• No external dependencies beyond database and message queue
• Kubernetes-ready with proper health checks

Real-World Notification Handling

Notifly handles the complexity of real-world notification delivery:

Provider Integration:

• Email: Brevo API for reliable email delivery
• SMS: Twilio for global SMS coverage
• Extensible: Easy to add new providers or notification types

Error Scenarios:

• Rate Limiting: Automatic backoff when providers throttle requests
• Provider Failures: Graceful degradation and retry strategies
• Invalid Recipients: Proper error classification and logging
• Network Issues: Resilient connection handling

Performance:

• Streaming Processing: Handle high message volumes without memory issues
• Configurable Batching: Balance throughput vs latency based on needs
• Worker Pools: Parallel processing where safe

Why Microservices for Notifications?

Some might argue this is over-engineering, but notifications have unique requirements:

Isolation: A bug in notification logic shouldn't bring down your main app Scaling: Different notification types have different performance characteristics
Technology Choice: Go's performance and reliability make sense for infrastructure Team Boundaries: Clear service boundaries enable independent development

The microservice approach also enables interesting patterns like A/B testing notification templates or gradual rollouts of new providers.

Development Experience

Working with Notifly feels natural:

Local Development: Docker Compose spins up the full stack locally. Add your API keys, run a few commands, and you're sending notifications.

API Design: GraphQL provides discoverability and type safety. The schema is intuitive - send a notification by specifying recipient, type, and content.

Testing: Each service can be tested independently. Mock providers make integration testing reliable.

Future Enhancements

Notifly works great today, but there's more planned:

• Template Management: Store and version notification templates
• Analytics Dashboard: Track delivery rates and engagement metrics
• Webhook Support: Send notifications via HTTP callbacks
• Push Notifications: Mobile and web push integration
• Scheduling: Send notifications at specific times or recurring intervals

The foundation is solid enough to support these features without architectural changes.