Notification System Fundamentals: Multi-Channel Fan-Out
Architect large-scale multi-channel notification engines: Push notifications (Apple APNs / Google FCM), SMS (Twilio), Email (AWS SES / SendGrid), in-app WebSockets, user preference matrices, rate-limiting spam guards, and dead-letter queues.
01.1. Architecture Requirements & Non-Functional Constraints
A production notification system must deliver billions of notifications across diverse communication channels with high reliability and low latency:
Functional Dimensions:
- Multi-Channel Dispatch: iOS/Android Push Notifications (Apple APNs, Google FCM), SMS (Twilio, MessageBird), Transactional Email (Amazon SES, SendGrid), and In-App WebSockets.
- User Preferences & Do-Not-Disturb (DND): Users must be able to toggle categories (e.g., Marketing vs Security Alerts vs Friend Activity) and define local timezone quiet hours (e.g., no promotional pushes between 22:00 and 08:00).
- Deduplication & Anti-Spam Frequency Capping: If a user receives 50 likes on a post within 10 seconds, the system must not blast 50 independent mobile push notifications. It must aggregate them into a single summary notification ("Alice and 49 others liked your post").
- Reliability & Idempotency: Critical transactional alerts (e.g., Two-Factor OTPs, fraud alerts, purchase receipts) must guarantee at-least-once delivery with strict sub-second SLAs (
< 1s).
Multi-Channel Notification Dispatch & Fan-Out Pipeline 🔔
Multi-Channel Notification Dispatch & Fan-Out Pipeline 🔔
Decoupled event ingestion, template hydration, user preference evaluation, rate limiting, channel-specific worker queues, and third-party gateway dispatch.
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