What are the most popular implementations of Kafka?
There are multiple implementations of Apache Kafka available for the customers. Popular ones that you may come across are 

- Open Source Implementations (VMs, K8s, Bare metal though rare): On-Prem and Cloud
- Confluent Kafka
- Azure EventHub with Kafka API
- Amazon MSK

Apache Kafka is the open source implementation of Kafka that can be deployed in your own infrastructure on-premises or in the cloud. It provides the core functionalities of Kafka and is the most widely used implementation.

Confluent is a company founded by the creators of Kafka that offers a complete Kafka distribution, along with additional features such as a schema registry, KSQL DB, Kafka Connect, and a management UI.

Azure Event Hubs is a cloud-based messaging service provided by Microsoft Azure that is fully compatible with Kafka. It offers a managed Kafka service as well as a native API.

Amazon MSK (Managed Streaming for Kafka) is a fully managed Kafka service offered by Amazon Web Services. It is fully compatible with Apache Kafka and provides seamless integration with other AWS services.