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nginx [engine x] is an HTTP and reverse proxy server, as well as a mail proxy server, written by Igor Sysoev. According to Netcraft nginx served or proxied 30.46% of the top million busiest sites in Jan 2018.

The Apache HTTP Server is a powerful and flexible HTTP/1.1 compliant web server. Originally designed as a replacement for the NCSA HTTP Server, it has grown to be the most popular web server on the Internet.

Firebase is a cloud service designed to power real-time, collaborative applications. Simply add the Firebase library to your application to gain access to a shared data structure; any changes you make to that data are automatically synchronized with the Firebase cloud and with other clients within milliseconds.

Apache Tomcat powers numerous large-scale, mission-critical web applications across a diverse range of industries and organizations.

Internet Information Services (IIS) for Windows Server is a flexible, secure and manageable Web server for hosting anything on the Web. From media streaming to web applications, IIS's scalable and open architecture is ready to handle the most demanding tasks.

It enables real-time bidirectional event-based communication. It works on every platform, browser or device, focusing equally on reliability and speed.

OpenResty (aka. ngx_openresty) is a full-fledged web application server by bundling the standard Nginx core, lots of 3rd-party Nginx modules, as well as most of their external dependencies.

It is a drop-in Apache replacement and the leading high-performance, high-scalability server. You can replace your existing Apache server with it without changing your configuration or operating system details. As a drop-in replacement, it allows you to quickly eliminate Apache bottlenecks in 15 minutes with zero downtime.

Phusion Passenger is a web server and application server, designed to be fast, robust and lightweight. It takes a lot of complexity out of deploying web apps, adds powerful enterprise-grade features that are useful in production, and makes administration much easier and less complex.

Gunicorn is a pre-fork worker model ported from Ruby's Unicorn project. The Gunicorn server is broadly compatible with various web frameworks, simply implemented, light on server resources, and fairly speedy.

Unlike other Ruby Webservers, Puma was built for speed and parallelism. Puma is a small library that provides a very fast and concurrent HTTP 1.1 server for Ruby web applications.

It is a simple to use, blazing fast, and thoroughly tested WebSocket client and server implementation.

Cowboy aims to provide a complete HTTP stack in a small code base. It is optimized for low latency and low memory usage, in part because it uses binary strings. Cowboy provides routing capabilities, selectively dispatching requests to handlers written in Erlang.

SignalR allows bi-directional communication between server and client. Servers can now push content to connected clients instantly as it becomes available. SignalR supports Web Sockets, and falls back to other compatible techniques for older browsers. SignalR includes APIs for connection management (for instance, connect and disconnect events), grouping connections, and authorization.

Pusher is the category leader in delightful APIs for app developers building communication and collaboration features.

An Application Server means, It can manage Java EE applications You should use GlassFish for Java EE enterprise applications. The need for a seperate Web server is mostly needed in a production environment.

Cloud Pub/Sub is a fully-managed real-time messaging service that allows you to send and receive messages between independent applications. You can leverage Cloud Pub/Sub’s flexibility to decouple systems and components hosted on Google Cloud Platform or elsewhere on the Internet.

Supabase is currently in early-Alpha .It is an open-source Firebase alternative. It adds realtime and RESTful APIs to your PostgreSQL database without a single line of code.

Jetty is used in a wide variety of projects and products, both in development and production. Jetty can be easily embedded in devices, tools, frameworks, application servers, and clusters. See the Jetty Powered page for more uses of Jetty.

Unicorn is an HTTP server for Rack applications designed to only serve fast clients on low-latency, high-bandwidth connections and take advantage of features in Unix/Unix-like kernels. Slow clients should only be served by placing a reverse proxy capable of fully buffering both the the request and response in between Unicorn and slow clients.

An application platform for hosting your apps that provides an innovative modular, cloud-ready architecture, powerful management and automation, and world class developer productivity.

Unlike traditional enterprise messaging systems, NATS has an always-on dial tone that does whatever it takes to remain available. This forms a great base for building modern, reliable, and scalable cloud and distributed systems.

Caddy 2 is a powerful, enterprise-ready, open source web server with automatic HTTPS written in Go.

OneSignal is a high volume push notification service for websites and mobile applications. OneSignal supports all major native and mobile platforms by providing dedicated SDKs for each platform, a RESTful server API, and a dashboard.

It is a coroutine -based Python networking library that uses greenlet to provide a high-level synchronous API on top of the libev or libuv event loop.

PubNub makes it easy for you to add real-time capabilities to your apps, without worrying about the infrastructure. Build apps that allow your users to engage in real-time across mobile, browser, desktop and server.

It is a flexible, lightweight, managed application runtime that helps you build amazing applications. It supports the latest standards for web development.

It is a family of free and open-source web application servers written in Python, and their associated online community. It stands for "Z Object Publishing Environment", and was the first system using the now common object publishing methodology for the Web

It is a lightning-fast ASGI server, built on uvloop and httptools. Until recently Python has lacked a minimal low-level server/application interface for asyncio frameworks. The ASGI specification fills this gap, and means we're now able to start building a common set of tooling usable across all asyncio frameworks.

lighttpd has a very low memory footprint compared to other webservers and takes care of cpu-load. Its advanced feature-set (FastCGI, CGI, Auth, Output-Compression, URL-Rewriting and many more) make lighttpd the perfect webserver-software for every server that suffers load problems.

An application server for building and deploying enterprise Java EE applications with support for new features for lowering cost of operations, improving performance, enhancing scalability and supporting the Oracle Applications portfolio.

It consists mainly of the Apache HTTP Server, MariaDB database, and interpreters for scripts written in the PHP and Perl programming languages.

Sanic is a Flask-like Python 3.5+ web server that's written to go fast. It's based on the work done by the amazing folks at magicstack. On top of being Flask-like, Sanic supports async request handlers.

It is built as a module for the Nginx web server. It can be configured as a standalone server, or as a shim between your application and hundreds, thousands, or millions of live subscribers. It can buffer messages in memory, on-disk, or via Redis.

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.

It is a highly scalable, secure and reliable Java EE runtime environment designed to host applications and microservices for any size organization. It supports the Java EE, Jakarta EE and MicroProfile standards-based programming models.

It is developed, tested, and supported as community-driven project by a diverse group of individuals and organizations. It is designed for interoperability, it publishes data from any major spatial data source using open standards.

NGINX Unit is a dynamic web application server, designed to run applications in multiple languages. Unit is lightweight, polyglot, and dynamically configured via API. The design of the server allows reconfiguration of specific application parameters as needed by the engineering or operations.

It is the centerpiece of the remote notifications feature. It is a robust, secure, and highly efficient service for app developers to propagate information to iOS (and, indirectly, watchOS), tvOS, and macOS devices.

Ably offers WebSockets, stream resume, history, presence, and managed third-party integrations to make it simple to build, extend, and deliver digital realtime experiences at scale.

It is an open source high-performance network framework using an event-driven, asynchronous, non-blocking I/O model which makes it scalable and efficient.

It is a flexible performant web server written in java, providing both blocking and non-blocking API’s based on NIO. It has a composition based architecture that allows you to build a web server by combining small single purpose handlers. The gives you the flexibility to choose between a full Java EE servlet 4.0 container, or a low level non-blocking handler, to anything in between.

GUN is a realtime, decentralized, embedded, graph database engine.

SocketCluster is a fast, highly scalable HTTP + realtime server engine which lets you build multi-process realtime servers that make use of all CPU cores on a machine/instance. It removes the limitations of having to run your Node.js server as a single thread and makes your backend resilient by automatically recovering from worker crashes and aggregating errors into a central log.

SurrealDB is a newsql multi-model database, that operates in schemafull or schemaless mode, with tables, inter-document record links (no JOINs), and graph database modelling functionality.

It Server is a drop in replacement for GlassFish Server Open Source Edition with quarterly releases containing enhancements, bug fixes and patches.

Scalable Server for Realtime Web Apps with JSON structures that can be read, manipulated and listened to, messages that can be sent to one or more subscribers, and request response workflows, between two clients or servers.

It is very lightweight profile of WebSphere Application Server. It is a flexible and dynamic profile of WAS which enables the WAS server to deploy only required custom features instead of deploying a big set of available JEE components.

It unlocks a new world of creativity for game developers by providing a cross-platform "backend-as-a-service" built exclusively for games. We give game developers the tools, technologies, and know-how they need to have a trouble-free launch day, and profitable day-to-day operations after that.

It is an open source backend for your next SaaS and mobile app in 1 file. It could be used as a standalone app or as a Go framework/toolkit that enables you to build your own custom app specific business logic and still have a single portable executable at the end.