Explain Message Queue vs Stream.

A message queue delivers each message once to a single consumer, while a message stream continuously broadcasts data events to multiple consumers in real time.

When to Use

• Message queues: Best for background jobs, order processing, or tasks that must run once reliably.
• Streams: Ideal for analytics, monitoring, and event-driven pipelines where multiple subscribers consume the same data.

Example

A message queue is like people waiting in line at a coffee shop (served one at a time). A stream is like a live radio broadcast where many listeners hear the same message instantly.

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Why Is It Important

Picking the right tool affects scalability.

Queues ensure reliable, ordered processing, while streams enable high-throughput, real-time insights.

Interview Tips

Be clear: queues = one consumer per message, streams = multiple consumers.

Reference tools like RabbitMQ, SQS, Kafka, or Kinesis to show practical knowledge.

Trade-offs

• Queues: Simple, reliable, but limited fan-out.
• Streams: Flexible, replayable, but harder to manage ordering and state.

Pitfalls

Using a queue where you need multiple consumers leads to duplication issues, while streams can be overkill for simple one-time tasks.