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Kafka is a distributed, partitioned, replicated commit log service. It provides the functionality of a messaging system, but with a unique design.

RabbitMQ gives your applications a common platform to send and receive messages, and your messages a safe place to live until received.

Transmit any volume of data, at any level of throughput, without losing messages or requiring other services to be always available. With SQS, you can offload the administrative burden of operating and scaling a highly available messaging cluster, while paying a low price for only what you use.

Celery is an asynchronous task queue/job queue based on distributed message passing. It is focused on real-time operation, but supports scheduling as well.

Apache ActiveMQ is fast, supports many Cross Language Clients and Protocols, comes with easy to use Enterprise Integration Patterns and many advanced features while fully supporting JMS 1.1 and J2EE 1.4. Apache ActiveMQ is released under the Apache 2.0 License.

It was designed as an extremely lightweight publish/subscribe messaging transport. It is useful for connections with remote locations where a small code footprint is required and/or network bandwidth is at a premium.

It is a cloud messaging system for connecting apps and devices across public and private clouds. You can depend on it when you need highly-reliable cloud messaging service between applications and services, even when one or more is offline.

An easy to use, powerful, and reliable system to process and distribute data. It supports powerful and scalable directed graphs of data routing, transformation, and system mediation logic.

It is a data streaming platform based on Apache Kafka: a full-scale streaming platform, capable of not only publish-and-subscribe, but also the storage and processing of data within the stream

The 0MQ lightweight messaging kernel is a library which extends the standard socket interfaces with features traditionally provided by specialised messaging middleware products. 0MQ sockets provide an abstraction of asynchronous message queues, multiple messaging patterns, message filtering (subscriptions), seamless access to multiple transport protocols and more.

It is free software/open-source .NET-based Enterprise Service Bus software that helps Microsoft developers route messages over MSMQ, RabbitMQ, TIBCO and ActiveMQ service busses, with native support for MSMQ and RabbitMQ.

NSQ is a realtime distributed messaging platform designed to operate at scale, handling billions of messages per day. It promotes distributed and decentralized topologies without single points of failure, enabling fault tolerance and high availability coupled with a reliable message delivery guarantee. See features & guarantees.

It is lightweight and is suitable for use on all devices from low power single board computers to full servers.. The MQTT protocol provides a lightweight method of carrying out messaging using a publish/subscribe model. This makes it suitable for Internet of Things messaging such as with low power sensors or mobile devices such as phones, embedded computers or microcontrollers.

It is a low-ambition library trying to solve a simple problem — decoupling the in-process sending of messages from handling messages. Cross-platform, supporting .NET Framework 4.6.1 and netstandard2.0.

It is a framework for building service-oriented applications. Using this, you can send data as asynchronous messages from one service endpoint to another. A service endpoint can be part of a continuously available service hosted by IIS, or it can be a service hosted in an application.

Apache Pulsar is a distributed messaging solution developed and released to open source at Yahoo. Pulsar supports both pub-sub messaging and queuing in a platform designed for performance, scalability, and ease of development and operation.

Gearman allows you to do work in parallel, to load balance processing, and to call functions between languages. It can be used in a variety of applications, from high-availability web sites to the transport of database replication events.

Performance, scalability, pub/sub, reliable integration, workflow orchestration, and everything else you could possibly want in a service bus.

It is a set of open technologies for instant messaging, presence, multi-party chat, voice and video calls, collaboration, lightweight middleware, content syndication, and generalized routing of XML data.

Fully managed, highly available RabbitMQ servers and clusters, on all major compute platforms.

Amazon MQ is a managed message broker service for Apache ActiveMQ that makes it easy to set up and operate message brokers in the cloud.

An end-to-end data integration platform to build, run, monitor and manage smart data pipelines that deliver continuous data for DataOps.

It is a Node.js library that implements a fast and robust queue system built on top of Redis. It is carefully written for rock solid stability and atomicity.

Apache RocketMQ is a distributed messaging and streaming platform with low latency, high performance and reliability, trillion-level capacity and flexible scalability.

Kestrel is based on Blaine Cook's "starling" simple, distributed message queue, with added features and bulletproofing, as well as the scalability offered by actors and the JVM.

An easy-to-use highly available message queuing service. Built for distributed cloud applications with critical messaging needs. Provides on-demand message queuing with advanced features and cloud-optimized performance.

This technology enables applications running at different times to communicate across heterogeneous networks and systems that may be temporarily offline. Applications send messages to queues and read messages from queues.

It is a distributed, fault-tolerant technology that allows the creation of large-scale instant messaging applications. The server can reliably support thousands of simultaneous users on a single node and has been designed to provide exceptional standards of fault tolerance.

VerneMQ is a distributed MQTT message broker, implemented in Erlang/OTP. It's open source, and Apache 2 licensed. VerneMQ implements the MQTT 3.1, 3.1.1 and 5.0 specifications.

It allows you to build stateful applications that process data in real-time from multiple sources including Apache Kafka.

DistributedLog (DL) is a high-performance, replicated log service, offering durability, replication and strong consistency as essentials for building reliable distributed systems.

A Node.js MQTT broker, which can be used as a Standalone Service or embedded in another Node.js application.

Disque is an ongoing experiment to build a distributed, in-memory, message broker. Its goal is to capture the essence of the "Redis as a jobs queue" use case, which is usually implemented using blocking list operations, and move it into an ad-hoc, self-contained, scalable, and fault tolerant design, with simple to understand properties and guarantees, but still resembling Redis in terms of simplicity, performance, and implementation as a C non-blocking networked server.

It is a socket library that provides several common communication patterns. It aims to make the networking layer fast, scalable, and easy to use. Implemented in C, it works on a wide range of operating systems with no further dependencies.

Highly scalable and effortless data streaming platform. Made to enable developers and data teams to collaborate and build real-time and streaming apps fast.

Starling is a powerful but simple messaging server that enables reliable distributed queuing with an absolutely minimal overhead. It speaks the MemCache protocol for maximum cross-platform compatibility. Any language that speaks MemCache can take advantage of Starling's queue facilities.

Hutch is a Ruby library for enabling asynchronous inter-service communication in a service-oriented architecture, using RabbitMQ.

Sparrow keeps messages in memory, but persists them to disk, using Sqlite, when the queue is shutdown.

It is a simple API to delay SQS messages. Call our APIs and we'll publish your messages when you need them.

It is a complete IoT Application suite with an inbuilt MQTT Broker. It is a perfect middleware for secure MQTT cloud & on premise deployment. It is the most affordable & fastest MQTT Broker to be used for collecting data from IoT edge devices & store & analyse it the way you need. Built on C & Python, MQTT Broker works with all standard MQTT clients and can readily manage & control your devices & will help you work on your core business challenge.

tl;dr: If you run a Redis server and currently use Amazon SQS or a similar message queue you might as well use this fast little replacement. Using a shared Redis server multiple Node.js processes can send / receive messages.

It is a distributed background task queue for Python backed by Redis, a super minimal Celery. Use it to run code in the background so your website stays fast and snappy, and your users stay happy.

A distributed, horizontally scalable, persistent, time ordered message queue. Developed to support asynchronous tasks and message scheduling which makes it suitable for usage as a task queue.

It is a hosted MQTT server solution to build a powerful industrial & commercial IoT applications. It is a secured MQTT server application which uses Bevywise MQTTRoute that comes with more options to deploy own AI/ML algorithms & customizable widgets to build own user interface.

It is an asynchronous distributed task queue for python. This project takes inspiration from big projects such as Celery and Dramatiq. It can send and run both the sync and async functions.

This tool enables a decoupled architecture, think sending emails when a user signs up. Instead of having explicit code in your signup function that does the work (and slows down your response), you just have to worry about inserting the row into the database.

It is a persistent message queue Go library built on SQLite and inspired by AWS SQS but much simpler. Messages are sent to and received from the queue, and are guaranteed to not be redelivered before a timeout occurs.

It is an open-source distributed message queueing framework, which focuses on efficiency, reliability, and a rich feature set for modern-day workflows.