Message Queues
A system that allows different parts of an application or different applications to communicate with each other by sending messages. It acts as a buffer between services, ensuring smooth, decoupled interactions and reliable message processing.
Why Use a Message Queue?
Imagine a distributed application with multiple servers handling various tasks. If one server crashes mid-task, you’d risk losing data. Storing tasks in a file or database is an option but it demands constant polling, leading to performance issues. A message queue solves this elegantly. Popular examples of messaging queues are RabbitMQ, Amazon SQS and Kafka.
Key Advantages -
- Decoupling of services
- Asynchronous communication (no need for both ends to be online simultaneously)
- Load balancing
- Reliability and fault tolerance
- Scalability
Example: Email Signup Workflow
- The Signup Service receives a new user registration and sends a message to the Email Queue.
- The Email Service consumes the message and sends a welcome email to the user.
- Meanwhile, the Analytics Service picks up the same message from a different queue to log the signup event.
Each service works independently, allowing the system to remain responsive and scalable even if email delivery or analytics take extra time.
Message Ordering Models
| Model | Description |
|---|---|
| Best-effort ordering | Messages are queued in the order they’re received (not guaranteed) |
| Strict ordering | Message sequence is tightly preserved, useful for ordered workflows |
Conclusion
Whether it’s handling requests, notifications, or critical backend events, message queues makes the modern microservice architecture possible.