Best Message-Oriented Middleware for KrakenD

RabbitMQ is lightweight, portable, and easy to use on the premises or in the cloud. It supports multiple messaging protocols. RabbitMQ can both be deployed in distributed or federated configurations to meet high availability and scale requirements.

Apache Kafka®, is an open-source distributed streaming platform.

Google Cloud Pub/Sub: Delivery of messages in large quantities with push and pull modes. Auto-scaling, auto-provisioning, support from zero to hundreds GB/second Independent quota and billing are available for subscribers and publishers. Multi-region systems can be simplified by global message routing High availability made easy: Ensure reliable delivery at all scales with synchronous, cross-zone message replication. Auto-everything, no-planning Auto-scaling, auto-provisioning without partitions eliminates the need for planning and ensures that workloads are ready for production from day one. Advanced features built in: Filtering, dead letter delivery, and exponential backoff all help to simplify your applications

Amazon Simple Notification Service is a fully managed messaging platform that allows for system-to–system and app-to–person (A2P), communication. It allows you to communicate between systems using publish/subscribe patterns (pub/sub), which allow messaging between decoupled microservice apps. You can also communicate directly with users via SMS, mobile push, and email. The system-to–system pub/sub functionality allows for topic-based, high-throughput push-based, many–to-many messaging. Your publisher systems can use Amazon SNS topics to fanout messages to large numbers of customer endpoints or subscriber systems, including Amazon SQS queues and AWS Lambda functions. You can send messages to large numbers of users using the A2P messaging functionality. This allows you to use either a pub/sub or direct-publish message using one API.