add: Solve challenge 1

[Mario1210m]

Selected challenge

I chose Challenge 1 because it allowed me to focus on transactional outbox, idempotent consumers, and eventual consistency trade-offs.

Key architectural decisions

• Used NestJS for the service structure and clear module boundaries.
• Implemented transactional outbox to avoid publishing directly inside the DB transaction.
• Added idempotency handling on the consumer side.
• Exposed a status endpoint that reflects eventual consistency honestly.

Alternatives considered

• Publishing directly to Kafka inside the transaction was rejected because it risks data loss and inconsistent state.
• A simpler synchronous approach was rejected because the challenge is centered on resilience and asynchronous processing.

What I would do with more time

• Add more integration and failure-recovery tests.
• Improve observability with tracing and metrics.
• Harden retry and DLT policies.

Known limitations / shortcuts

• Local-only setup assumptions.
• Simplified operational configuration for the sake of the exercise.
• Some production-grade concerns could be expanded further.