Requirements & Scope
Email Flow
- Event triggers email request
- Render template (Thymeleaf)
- Queue to Kafka
- Worker sends via SES/SendGrid
- Webhook receives delivery status
- Update status in database
Scale
- 1M emails/day, 500/sec peak
- 99%+ delivery rate
Key Points
- Understanding Email Notification Service is essential for production systems
- Always consider scalability and maintainability
- Test thoroughly before deploying to production
- Monitor performance and set up alerting
Common Patterns
- Validation: Always validate input at the boundary
- Error Handling: Use structured error responses
- Logging: Log key events for debugging
- Testing: Unit, integration, and load tests
- Documentation: Keep docs updated with code changes
Architecture & Pipeline
Async Processing
Queue emails to prevent failures from impacting user requests.
Bounce Handling
- Hard bounce: mark invalid, suppress future sends
- Soft bounce: retry up to 3 times
- Complaint: suppress
Rate Limiting
- SES: 200/sec (sandbox: 1/day)
- Monitor queue depth for backpressure
Key Points
- Understanding Email Notification Service is essential for production systems
- Always consider scalability and maintainability
- Test thoroughly before deploying to production
- Monitor performance and set up alerting
Common Patterns
- Validation: Always validate input at the boundary
- Error Handling: Use structured error responses
- Logging: Log key events for debugging
- Testing: Unit, integration, and load tests
- Documentation: Keep docs updated with code changes
Delivery Tracking
Tracking Pipeline
Provider webhooks (SES, SendGrid) report delivery events in real time. Each event is stored in the email_events table with the raw JSONB payload for auditing.
Tables
- emails(id, to_address, subject, template, status, provider_message_id, sent_at, delivered_at, opened_at, clicked_at)
- email_events(id, email_id, event_type, payload JSONB)
Event Types
- delivered: message reached recipient inbox
- opened: recipient loaded tracking pixel
- clicked: recipient clicked a link in the email
- bounced: delivery failed (hard or soft)
- complained: recipient marked as spam
Practice Problems
Design and implement a solution for Email Notification Service in a backend system. Consider scalability, error handling, and production readiness.
Solution
// Email Notification Service implementation
// Key aspects: validation, error handling, logging, testing
public class EmailNotificationService {
// Production-ready implementation
}Identify and handle edge cases for Email Notification Service. What happens under high load, with invalid input, or during failures?
Solution
// Edge case handling:
// 1. Null/empty input -> validation
// 2. High load -> rate limiting, queuing
// 3. Failures -> retries, circuit breaker
// 4. Concurrent access -> locks, idempotencyWrite a testing strategy for Email Notification Service. Include unit tests, integration tests, and performance tests.
Solution
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injectionQuiz
1. Why queue emails async?
2. Hard bounce action?
3. What is the primary purpose of Email Notification Service?
4. What is a common mistake when implementing Email Notification Service?
Flashcards
Question
Why queue emails?
Click to reveal answer
Answer
Async processing, retries, non-blocking
Question
Hard bounce action?
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Answer
Mark invalid, suppress future sends
Question
What is Email Notification Service?
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Answer
Email Notification Service is a key concept in backend development.
Question
When to use Email Notification Service?
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Answer
Use Email Notification Service when building production systems that require reliability, scalability, and maintainability.
Question
Email Notification Service best practices
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Answer
Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.
Revision Notes
Key Takeaways
- 1.Queue for async processing
- 2.Track via provider webhooks
- 3.Suppress hard bounces
- 4.Rate limit within provider limits
Interview Tips
- •Explain full email pipeline
- •Discuss bounce handling
Cheat Sheet
Email Service
- Pipeline: Trigger -> Template -> Queue -> Send -> Track
- Bounces: Hard=suppress, Soft=retry
- Rate Limit: Stay within SES/SendGrid limits