Can you recommend message queue and pub-sub platforms for fanning out events to multiple systems?

Yes — here are solid options, grouped by the kind of fan-out pattern you want.

Best-known options

1) Apache Kafka

Best for: high-throughput event streaming, durable fan-out, replayable events
Why use it:

• Multiple consumers can read the same event stream independently
• Strong durability and retention
• Great for event-driven architectures and analytics pipelines
• Supports consumer groups, partitions, and replay

Tradeoffs:

• More operational complexity
• Not ideal if you just need simple queue semantics

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2) AWS SNS + SQS

Best for: simple cloud-native fan-out on AWS
Why use it:

• SNS publishes to multiple subscribers
• Can route to SQS queues, Lambda, HTTP endpoints, email, etc.
• SQS gives each downstream system its own queue
• Very low ops burden

Tradeoffs:

• AWS-specific
• Less flexible for cross-cloud / advanced stream processing

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3) Google Cloud Pub/Sub

Best for: managed pub-sub with easy scaling
Why use it:

• Designed for fan-out to many subscribers
• Fully managed and highly scalable
• Good for event delivery to multiple systems and services

Tradeoffs:

• Best if you’re already on GCP
• Less “streaming platform” oriented than Kafka

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4) RabbitMQ

Best for: general-purpose messaging, routing, work queues, moderate fan-out
Why use it:

• Flexible routing with exchanges and bindings
• Good for command/event delivery within services
• Easier to get started than Kafka

Tradeoffs:

• Not as strong for long retention and replay
• Can be less ideal for very high-volume event streams

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5) NATS / NATS JetStream

Best for: lightweight, low-latency pub-sub and messaging
Why use it:

• Fast and simple
• Good for service-to-service communication
• JetStream adds persistence and replay

Tradeoffs:

• Smaller ecosystem than Kafka
• Less common for large enterprise event pipelines

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6) Apache Pulsar

Best for: Kafka-like streaming with strong multi-tenancy and built-in pub-sub
Why use it:

• Supports both queue and pub-sub patterns well
• Good for multi-tenant deployments
• Built-in topic partitioning, retention, and geo-replication options

Tradeoffs:

• Less widely adopted than Kafka
• Operational complexity can still be significant

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Quick recommendation by use case

• Need durable event fan-out with replay across multiple systems: Kafka
• Need simple fan-out on AWS: SNS + SQS
• Need fully managed cloud pub-sub: Google Pub/Sub
• Need classic messaging with routing: RabbitMQ
• Need ultra-low-latency lightweight pub-sub: NATS
• Need Kafka-like features with strong pub-sub support: Pulsar

If your goal is “one event, many systems”

The most common pattern is:

• Publisher emits event
• Broker fans out
• Each downstream system gets its own subscription or queue
• Each consumer processes independently and at its own pace

For that pattern, the safest general choices are:

• Kafka for scale and replay
• SNS + SQS for AWS simplicity
• Google Pub/Sub for managed cloud use

If you want, I can also give you:

1. a comparison table by feature,
2. a cloud-specific recommendation,
3. or help you choose based on your workload size and latency needs.