TL;DR ⚡
Abstract
- Message queue = the data structure/channel (messages line up, usually point-to-point).
- Message broker = the whole middleware that manages queues + topics, adds routing, pub/sub, delivery guarantees.
- The queue is one mechanism inside the broker. (Your intuition was right — not the same.)
- Kafka a must for Saga/CQRS? No — both are patterns; any transport (Kafka, RabbitMQ, REST) works.
Queue vs Broker (they’re not synonyms)
- Message queue — a channel where messages line up; a consumer takes them. Classic queue = point-to-point (one message → one consumer).
- Message broker — the middleware system that hosts many queues/topics and adds routing, pub/sub fan-out, transformation, delivery guarantees, persistence.
- Relationship: a broker contains queues (and topics). RabbitMQ is a broker; a queue is a thing it holds.
Two messaging styles
- Point-to-point (queue): one message consumed by exactly one consumer. Work distribution.
- Publish/subscribe (topic): one message fanned out to many subscribers. Events.
Where Kafka fits
Kafka is often called a broker, but it’s really a distributed append-only log (topics split into partitions). Consumers read at their own offset, so the same message can be read by many consumer groups — that’s why it fans out like pub/sub and retains messages. Not a classic “consume-and-delete” queue.
Is Kafka required for Saga / CQRS?
No. Both are patterns, tool-agnostic:
- Saga needs steps to communicate — Kafka, RabbitMQ, or even synchronous REST calls.
- CQRS needs writes propagated to the read model — Kafka, a DB trigger, or a batch job.
Kafka is a common implementation choice, never a requirement.
Test Yourself
Message queue vs message broker?::Queue = the channel where messages line up (often point-to-point). Broker = the middleware managing queues/topics with routing, pub/sub, guarantees. Queue is inside the broker.
Is Kafka a queue?::Not classic — it’s a distributed log (topics + partitions); consumers read at offsets, many groups can read the same messages (pub/sub-like, retained).
Is Kafka required for Saga or CQRS?::No — both are tool-agnostic patterns; any transport (Kafka, RabbitMQ, REST, DB trigger, batch) works.
Point-to-point vs pub/sub?::Point-to-point = one message → one consumer (queue). Pub/sub = one message → many subscribers (topic).