API Events

The only async surface is one CDC consumer. There are no Kafka producers, BullMQ queues, or WebSocket emissions.

1. Inbound — Kafka

Topic	Producer	Handler	Idempotency Key	Failure Mode
public.Product (CDCKafkaTopics.PRODUCT)	Debezium (commerce)	TaxationWorkerService.handleProductCDC	(productId, taxGroupId, op) — provision is idempotent	log + skip (autocommit; no DLQ)

Consumer config (ApplicationKafkaComponent):

Setting	Value
Client ID	APP_ENV_KAFKA_CLIENT_ID (default SVC-00130-TAXATION_CONSUMER)
Group ID	APP_ENV_KAFKA_GROUP_ID (default SVC-00130-TAXATION_CONSUMER_GROUP)
Key deserializer	stringDeserializer
Value deserializer	jsonDeserializer
fallbackMode	latest (no historical backfill)
autocommit	true
requestTimeout / connectTimeout / maxWaitTime	60000 / 30000 / 5000 ms

Op routing:

Debezium op	Action
c, u, r	_reconcileTaxProvisions(after)
d	deprovisionForProduct(before.id ?? after.id)
other	ignored

Reconcile branch (c/u/r):

Product state	Action
deletedAt set	deprovision
no taxGroupId	deprovision
taxGroupId present	provision (idempotent)

2. Outbound — Kafka

None. Taxation does not produce events. Provisioned TaxSet/Tax rows are read by pricing directly from the shared DB.

3. Inbound — BullMQ

None.

4. Outbound — BullMQ

None.

5. WebSocket Emissions

None.

6. Payload Schemas

Inbound payload is a Debezium envelope around a Product row. Types are from @nx/core (TDebeziumMessage, TDebeziumPayload, TProductPgRow). Snake_case row keys are converted via toCamelCaseKeys before use.

// CDCKafkaTopics.PRODUCT — message.value
interface TDebeziumMessage<TProductPgRow> {
  payload: TDebeziumPayload<TProductPgRow>;
}

interface TDebeziumPayload<T> {
  op: 'c' | 'u' | 'r' | 'd';
  before: T | null; // snake_case
  after: T | null;  // snake_case
}

// Fields read by the worker (post toCamelCaseKeys):
//   id: string
//   taxGroupId: string | null
//   deletedAt: string | null

7. Idempotency & Ordering

Topic	Delivery	Ordering	Recovery
public.Product	at-least-once (autocommit)	per-partition (per product key)	re-deliver replays reconcile; provision skips when already provisioned with the same TaxGroup

No DLQ: onMessageError logs only. fallbackMode: latest means rows changed while the consumer was down before the offset window are not reprocessed — there is no backfill job (ADR-0001).

8. Related Pages

• Integration
• Architecture — Runtime Scenarios