Amazon SQS vs Celery vs Kafka: What are the differences?

## Introduction
When comparing Amazon SQS, Celery, and Kafka, it is important to understand the key differences between these popular messaging systems.

## 1. Scalability:
Amazon SQS is a fully managed service in the cloud, which makes it highly scalable and able to handle large amounts of message traffic with ease. Celery, on the other hand, requires manual configuration and management to achieve scalability. Kafka is also designed for high scalability and can handle millions of messages per second.

## 2. Message Retention:
Amazon SQS has a default retention period of 4 days, which can be extended up to 14 days. Celery allows for customization of message retention based on configuration settings. In contrast, Kafka retains messages for a configurable amount of time, making it highly flexible in managing message retention.

## 3. Message Delivery Guarantees:
Amazon SQS offers at-least-once message delivery guarantees, meaning messages will be delivered to consumers at least once. Celery provides customizable delivery guarantees, ranging from at-most-once to exactly-once delivery semantics. Kafka offers strong durability guarantees and supports exactly-once delivery semantics out of the box.

## 4. Message Ordering:
Amazon SQS does not guarantee message ordering, as messages can be processed out of order. Celery supports message ordering through the use of task queues, ensuring that tasks are executed in the order they were added. Kafka provides strong support for message ordering and guarantees that messages within the same partition will be delivered in order.

## 5. Resource Management:
Amazon SQS handles resource management automatically, allowing users to focus on building applications without worrying about infrastructure. Celery requires manual resource management, including setting up and maintaining worker processes. Kafka also requires manual resource management, but provides tools for partitioning and replication for efficient resource utilization.

## 6. Latency and Throughput:
Amazon SQS has variable latency depending on the load and network conditions, with limited throughput per queue. Celery offers lower latency and higher throughput compared to Amazon SQS due to its efficient task queuing system. Kafka provides low latency and high throughput for real-time data processing, making it suitable for high-performance use cases.

In Summary, Amazon SQS, Celery, and Kafka differ in scalability, message retention, delivery guarantees, message ordering, resource management, and latency/throughput characteristics.