Why should you care?

When invoice service is down, order service still publishes events; RabbitMQ buffers until consumer recovers.

See it live — copy this example

Paste into your MeanVerse project (Angular + Express + MongoDB), then run with ng serve / node / mongosh as noted.

import amqp from 'amqplib';

const conn = await amqp.connect(process.env.RABBIT_URL!);
const ch = await conn.createChannel();
await ch.assertExchange('meanverse.events', 'topic', { durable: true });

// publisher (orders)
ch.publish('meanverse.events', 'order.created', Buffer.from(JSON.stringify({ orderId, tenantId })), { persistent: true });

// consumer (billing)
await ch.assertQueue('billing.order-created', { durable: true });
await ch.bindQueue('billing.order-created', 'meanverse.events', 'order.created');
ch.consume('billing.order-created', msg => { /* create invoice */ ch.ack(msg!); });

What happened?

• topic exchange routes by routing key pattern.
• persistent messages survive broker restart.
• ack after successful processing prevents message loss.

Practice next

1. Define event naming: entity.action.
2. Use durable queues and persistent messages.
3. build dead-letter queue for poison messages.
4. Add priority queue for fraud alerts.
5. Monitor queue depth alerting > 10k.

Remember

RabbitMQ = reliable async messaging. Topic routing flexible for many consumers. Decouples MeanVerse service availability.

Order to invoice

Order placed event triggers billing, email, analytics independently.

Outcome: Three consumers on one event; add fourth without changing order API.