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Phase 7 — Concurrency Scenarios (Reactive & Virtual Threads)

🏷️ Domain Focus

Primary: 🏪 eCommerce - Checkout and inventory streaming
Secondary: 💬 Chat (SSE/WebSocket), 📱 Social (Feed streaming), 🏭 IoT (Batch processing)
Architecture Reference: 01-ARCHITECTURE/domains/ecommerce/DOMAIN_ECOMMERCE_ARCHITECTURE.md
Protocol Focus: 🔄 SSE/WebSocket streaming, 🔗 Webhooks, ⚡ Concurrency patterns

Objectives

  • Implement A/B concurrency scenarios for learning and selection.
  • Learning Focus: Modern Java concurrency - Reactive Programming vs Virtual Threads, WebSockets/SSE, Webhooks.

Deliverables - Reactive checkout; streaming inventory; VT webhooks; VT replay - A/B comparison notes and architectural decision

Tasks (acceptance)

1) Reactive Checkout (Scenario A - Reactive Learning) - [ ] Non-blocking REST calls; R2DBC; resilience configured - [ ] Practice Reactor operators: flatMap, zip, timeout, retryBackoff - [ ] Use StepVerifier for testing reactive flows - [ ] Implement backpressure handling - [ ] 🏪 eCommerce Focus: order-service + payment-adapter-service

2) Streaming Inventory (Protocol Labs - SSE/WebSockets) - [ ] SSE + WebSocket notifications; basic load test - [ ] Practice fan-out patterns with Flux.share() - [ ] Implement heartbeat and reconnection strategies - [ ] Add authentication and authorization for streams - [ ] 🏪 eCommerce: inventory-service stock updates - [ ] 💬 Chat: Real-time message delivery patterns - [ ] 📱 Social: Live feed updates with SSE

3) VT Webhooks (Scenario C - Virtual Threads Learning) - [ ] VT executor; bounded concurrency; tracing - [ ] Practice structured concurrency patterns - [ ] Implement HMAC signature verification - [ ] Add per-partner rate limiting and bulkheads - [ ] 🏪 eCommerce: partner-webhook-dispatcher service

4) VT Replay (Scenario D - Batch Processing) - [ ] Batch replay with backoff and checkpoints - [ ] Practice file processing with virtual threads - [ ] Implement resumable processing with state management - [ ] 🏭 IoT: Batch telemetry processing - [ ] 🧠 ML/AI: Feature batch processing 5) Protocol Integration - [ ] Webhook protocol lab: implement retry policies - [ ] WebSocket protocol lab: handle connection lifecycle - [ ] SSE protocol lab: implement Last-Event-ID support 6) Docs & Comparison - [ ] Document A/B comparison with performance metrics - [ ] Create ADR documenting concurrency model choice - [ ] Update protocol examples with lessons learned

Dependencies - Phase 6

Learning & References - Reference Topics (Protocols & Concurrency)

Next Phase: Phase 8