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Lessons (14)

• Design a Reliable Notification System

  Deliver email, SMS, push and in-app messages with preferences, isolation, idempotency, provider failover and auditable states. ![Notification …

• Creational Patterns: How to Make Objects

  … one place that knows how to create notifiers function createNotifier(type) { const Notifier = notifiers[type]; if (!Notifier) throw …

• SOLID at a Glance

  … injected abstractions this.repository = repository; this.notifier = notifier; } async publish(report, exporter) { const file = exporter.export(report); // L …

• Hexagonal Architecture (Ports & Adapters)

  … LoanRepository, private readonly notifier: Notifier, private readonly clock: Clock, ) {} async borrow(memberId: string, bookId: string): Promise<Loan { if …

• KISS: Keep It Simple, Stupid

  … welcomeTemplate(user) }); } When you have five notification channels, a strategy pattern may earn its place. With one, it …

• Event-Driven Architecture

  … Event notification Just "something happened" + an ID { type: "OrderPlaced", orderId: "o42" } ; consumers call back for details Tiny events …

• Design a Chat Application

  Deliver live messages without losing them by separating durable messages from fan-out, presence and offline notifications. ![Chat …

• Real-Time, Pub/Sub, Webhooks and CDC

  … One-way stream; reconnect with event ID Webhook Notify another server Sign, retry and make receiver idempotent WebRTC …

• Behavioral Patterns I: Observer, Strategy, Command, State

  … You subscribe once; every new video, you get notified. The channel doesn't know or care who you …

• What Are Design Patterns?

  … S["💡 Solution<br/ subscribers register;<br/ the subject notifies them"] S -- C["⚖️ Consequences<br/ loose coupling, but<br …

• React vs Vue vs Angular

  … signals (+ zone.js legacy)"] A1[signal changes] -- A2[dependents are notified] -- A3[update affected views] end - React re …

• Service Communication: Sync vs Async

  … REST / gRPC] Q1 -- no Q2{Is it a notification<br/ that something happened?} Q2 -- yes Ev[Publish an …

• Caching & Redis

  … consumer groups Pub/Sub PUBLISH , SUBSCRIBE Real-time notifications, chat js // Leaderboard in 3 commands await redis.zAdd …

• Domain-Driven Design: Strategic Design

  … whenever… then…") 🟪 Lilac Whenever payment fails, then notify the customer External system 🩷 Pink Stripe Hot spot …