Epic: Eventual Consistency and Race Condition Mitigation Across AWS Regions

[KeveenMenezes]

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Epic Title:
Eventual Consistency and Race Condition Mitigation Across AWS Regions

Problem Statement:
DuckStore experiences heavy asynchronous order, inventory, and account updates across distributed AWS regions. Guaranteeing eventual consistency and preventing race conditions, lost updates, and out-of-order delivery during network partitions and traffic spikes becomes increasingly difficult. Recent failures have resulted in regionally inconsistent shopping carts, stale inventory, and duplicate orders from out-of-sequence event processing.

Architectural Context:

• .NET 10 microservices, async event-driven messaging (Kinesis, SQS, EventBridge)
• Distributed state, no single source of truth
• Multi-env (prod/staging/dev), AWS regions

Constraints:

• No synchronous fallback for inventory or checkout; replay logic cannot assume ordering.
• Duplicate and partial message deliveries need to be handled gracefully.
• External SLAs on consistency from downstream providers

Non-Functional Requirements:

• SLA: 99.99% consistency within 5 minutes for inventory/order state across regions
• No data loss in region failover scenarios
• Region-specific reconciliation tooling and metrics

Acceptance Criteria:

• Consistency strategy documented and validated under ambiguous and deterministic failures
• Race condition handling/mechanisms proven via simulation/integration tests
• Playbook for regional failover and healing

Risk Areas:

• Race conditions during partition healing
• Event replay causing duplicate orders/inventory loss
• Visibility lag affecting user experience

Suggested Research Topics:

• CRDTs vs. event sourcing for state convergence
• Idempotency and deduplication strategies for distributed event consumers
• Automated reconciliation tooling in cloud-native .NET

Difficulty Level: Architect-Level