How a Brazilian startup built fan-out on BullMQ without adding a message broker

The CTO of Monest, a Brazilian debt-collection startup running a NestJS backend, faced a fan-out problem when multiple teams and client integrations all needed to react to the same 'tag applied' event in real time. BullMQ, their existing job queue, is designed for one-event-one-consumer processing and does not natively support delivering a single event to multiple listeners. Rather than introducing a dedicated message broker like RabbitMQ or Kafka — which would add infrastructure, operational overhead, and on-call complexity for a lean team — the team evaluated what BullMQ was actually failing at and found it was only one narrow gap. Their solution was to keep a single tag-applied worker that sequentially calls all downstream handlers, effectively achieving fan-out without any new infrastructure.