Kafka vs RSMQ: What are the differences?

# Introduction
Here are the key differences between Kafka and RSMQ:

1. **Message Ordering**: Kafka guarantees ordered message delivery within a partition while RSMQ does not ensure message order within a queue. This means that in Kafka, the messages are always consumed in the order they are produced, whereas in RSMQ, messages can be consumed out of order.
2. **Message Retention**: Kafka stores messages in a durable and fault-tolerant manner, with the ability to retain messages for a specified period. On the other hand, RSMQ is a simple message queue that does not provide built-in message retention policies, potentially leading to data loss if not handled properly.
3. **Scalability**: Kafka is designed for high-throughput and scalability, allowing for horizontal scaling with multiple brokers in a cluster. RSMQ, while efficient for small-scale applications, may face limitations in scaling to handle large volumes of data and high concurrency requirements.
4. **Fault Tolerance**: Kafka is resilient to node failures as it replicates partitions across multiple brokers, ensuring high availability and fault tolerance. In contrast, RSMQ may not provide the same level of fault tolerance, especially in single-node setups where a failure can lead to message loss.
5. **Message Persistence**: Kafka persists messages to disk, ensuring that messages are not lost even in the event of system failures. RSMQ, being an in-memory message queue, may lose messages if the server crashes or restarts, making it less suitable for critical data durability requirements.
6. **Complexity**: Kafka is a feature-rich distributed messaging system with robust functionality for stream processing and event-driven architectures, making it more complex to set up and manage compared to the lightweight and straightforward RSMQ solution, which caters to simpler messaging needs.

In Summary, Kafka offers ordered message delivery, strong message retention policies, scalability for high-throughput applications, fault tolerance against node failures, message persistence to disk, and a feature-rich but complex design. On the other hand, RSMQ provides simplicity, lacks strict message ordering guarantees, limited message retention options, scalability challenges for large volumes of data, lower fault tolerance without replication, potential for message loss on server crashes, and a lightweight architecture suitable for basic messaging requirements.