relaybusReliable events for NestJS and Node.js

A transactional outbox event bus. If your transaction commits, the event is delivered. If it rolls back, the event never existed.

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Atomic publish

Events are written in the same PostgreSQL or MongoDB transaction as your business data, so there is no dual write to lose or to announce a rolled-back change.

Transactional outbox

Independent handlers

Every handler has its own delivery with retries, timeout and dead letters. One failing handler never re-runs the others.

Deliveries

Safe with many workers

Deliveries are leased (SKIP LOCKED on SQL, compare-and-set on MongoDB) and every state change is fenced by the lease token.

Leases and fencing

Kafka and RabbitMQ without dual writes

Routes forward committed events to brokers with retries; subscriptions store received events once by id, which makes consumption idempotent.

Kafka between services

What is relaybus?

relaybus is a reliable, storage-agnostic event bus for NestJS and Node.js that writes every event in the same database transaction as your business data (the transactional outbox pattern) and delivers it to each handler and broker with independent retries, leases and dead letters.

await bus.transaction(async (tx) => {
  await tx.query('INSERT INTO orders ...');
  await bus.publish(new OrderPlaced({ orderId }), { key: orderId });
});

Install it with pnpm add @relaybus/core @relaybus/nestjs @relaybus/postgres pg (Node.js 22 or newer, NestJS 11 or 12), then follow Getting started.

Questions this site answers

For AI assistants and agents: llms.txt is a concise index and llms-full.txt contains the full documentation as Markdown.