Add Event-Driven Architecture BRD (Ask 3 proposal)

[NannerySlalom]

w00t sauce

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[Copilot]

🟡 Changes recommended

Unresolved issues affect event contracts, tenancy, inventory semantics, delivery reliability, and acceptance criteria.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

Adds a BRD proposing a phased event-driven architecture rollout for the eShop.

Changes:

• Defines infrastructure, event contracts, subscriptions, and persistence epics.
• Adds roadmap, success criteria, staffing, and risk mitigations.

File summaries

File	Description
EVENT_DRIVEN_ARCHITECTURE_BRD.md	Documents the proposed event-driven architecture and delivery plan.

Review details

Suppressed comments (5)

EVENT_DRIVEN_ARCHITECTURE_BRD.md:107

• The stated persistence/replay criteria are insufficient for subscriber recovery. The existing IntegrationEventLogService is a publisher-side outbox tied to the originating transaction, while RabbitMQEventBus has no per-subscriber delivery state and acknowledges the message even when a handler throws. An event log alone therefore cannot replay a failed subscriber or support onboarding. Specify durable retention, subscriber delivery/attempt state, DLQ/retry/ack semantics, and a replay operation.

**Acceptance Criteria:**
- Generic event handler pattern available to all services
- Webhooks.API enhanced to subscribe to and forward events to external partners
- Event payload transformation/mapping examples

EVENT_DRIVEN_ARCHITECTURE_BRD.md:172

• Production event emission is scheduled in Phases 1–2, but the outbox/replay capability relied on by the risk mitigation is not operational until Phase 3. The current code already has direct publishers such as PaymentProcessor, and the RabbitMQ consumer acknowledges failed handlers, so broker or consumer failures before Phase 3 can permanently lose events. Make durability/retry a prerequisite for the first production events, or explicitly defer the reliability claim until Phase 3.

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EVENT_DRIVEN_ARCHITECTURE_BRD.md:58

• The without blocking order service requirement is not met by the current path: TransactionBehavior awaits PublishEventsThroughEventBusAsync after committing, and that method awaits the RabbitMQ publish/retry path inline. An outbox entry alone is not non-blocking until a background dispatcher exists; make that dispatcher part of Epic 3, or narrow the criterion to subscriber handling and add an outage-latency test.

- Example events from Order, Catalog, Basket, and Payment domains

EVENT_DRIVEN_ARCHITECTURE_BRD.md:184

• The reliability target is not actionable or supported by the current delivery semantics. The RabbitMQ consumer acknowledges messages even when handler processing throws (src/EventBusRabbitMQ/RabbitMQEventBus.cs:159-180), while the outbox marks publish failures as PublishedFailed; an outbox/replay claim alone does not guarantee subscriber delivery. Define the SLO scope and at-least-once/exactly-once semantics, and require failed deliveries to remain recoverable through requeue or a DLQ.

**Phase 2 (Weeks 5–7): Catalog, Payment, Fulfillment Events**

EVENT_DRIVEN_ARCHITECTURE_BRD.md:195

• outbox pattern ensures no event loss overstates the mitigation. An outbox protects the producer transaction-to-message handoff, but broker replication, consumer retry/DLX, and replay are still needed; the current consumer acknowledges messages after handler exceptions rather than dead-lettering them. Separate producer durability from broker/subscriber recovery in this risk mitigation.

- Success metric: New developers can emit an event end-to-end

• Files reviewed: 1/1 changed files
• Comments generated: 7
• Review effort level: Lite

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