Async processing

Two durable mechanisms and one that does not survive a crash.

Mechanism	Process	Survives process crash
Prisma outbox, then EventEmitter2	Dispatcher only on the worker	Yes. The row commits with the business write
Bull queue	Worker processors	Yes. Redis
EventEmitter2.emit inside the API	Listeners loaded in that process	No

Do not replace an outbox enqueue with an in-process emit for order side effects. A listener registered only on the worker will not see an API emit, and the emit is not transactional.

Dispatcher

OutboxDispatcherService:

Behavior	Value read
Poll	Every 1 second
Claim	Batch 100, FOR UPDATE SKIP LOCKED
Dispatch concurrency	10
Success	Status PROCESSED
Listener throw	Attempts increment, stay PENDING until 10, then DEAD. lastError stored
Backoff	min(60_000, 2^attempts * 1000) ms
Stale PROCESSING	Older than 5 minutes returns to PENDING without incrementing attempts
Purge	PROCESSED older than 30 days, batches of 5000, max 20 batches. Cron 03:00
ProcessedEvent purge	Older than 90 days, same batching

emitAsync waits for listeners. If any listener rejects, the promise rejects and the event stays retryable, so all listeners run again. A listener that already succeeded and is not idempotent will double-apply. IdempotentEventHandlerService exists and is opt-in. It locks the order row when orderId is provided and records ProcessedEvent. Which listeners call it was not fully enumerated.

DEAD rows are not automatically returned to PENDING. The replay procedure is unknown.

In-process events that are not outbox types

Name	Producer	Listener found
channel.created	ChannelService	channel location auto-bind
channel.updated	ChannelService	webhook health
audit.log	audit interceptor, WooCommerce webhook health	AuditLogListener
product.content.changed	product event publisher	ProductEmbeddingListener
product.channel-allocation.changed	product events	ProductStockSyncListener
shipment.status.changed	shipment services	fulfillment, NDR, return shipment
return.status.changed	return command	none
return.stock.restored	return inventory	none

No consumer

return.status.changed and return.stock.restored are emitted. No @OnEvent listener was found. Nothing retries them.

Details: Events and Queues.