Open-source alternatives to Async

Quasar is a JVM concurrency framework that implements the actor model and a lightweight thread library. It provides isolated execution units that communicate via asynchronous message passing to eliminate shared mutable state. The project distinguishes itself through a distributed actor system capable of operating across multiple cluster nodes with location-transparent registries and actor state migration. It utilizes a work-stealing fiber scheduler to manage millions of lightweight threads, allowing tasks to suspend during non-blocking I/O operations without stalling underlying system threads

Trio is an asynchronous I/O runtime and concurrency library for Python. It provides a system for executing non-blocking network and disk operations through a centralized event loop and task scheduler. The library is built on a structured concurrency model, which ensures that asynchronous tasks are bound to a specific lifetime and cannot outlive the scope that started them. It utilizes a nursery-based task manager to track task lifecycles in a parent-child tree, preventing orphaned concurrent operations by requiring child tasks to be joined before their parent scope exits. The framework cover

Arrow is a functional programming library for Kotlin that provides tools for implementing data-oriented programming patterns. It serves as a framework for typed error handling, a concurrency toolkit, and a library for the manipulation of immutable data. The project distinguishes itself through specialized capabilities for managing application failures using explicit types instead of exceptions and implementing resilience patterns such as circuit breakers and retry policies for distributed services. It also provides optics to update and query deeply nested immutable data structures without man

Swift NIO is a low-level, event-driven network framework for the Swift language. It serves as an asynchronous network protocol stack and I/O library designed to build high-performance network servers and clients that handle thousands of simultaneous connections. The framework functions as a high-concurrency network engine that dispatches events across multiple CPU cores. It enables the implementation of custom network protocols by processing raw bytes through a sequence of reusable data transformation handlers. The system provides capabilities for non-blocking I/O multiplexing, asynchronous

ZIO is a functional effect system for the JVM that models asynchronous and concurrent programs as pure, composable values with typed error handling and dependency injection. Its core identity is built on fiber-based concurrency, where lightweight, non-blocking fibers execute millions of concurrent tasks with structured lifecycle management, and a dual-channel error model that separates expected business failures from unexpected system defects at compile time. The system provides effect-typed dependency injection through a layer-based dependency graph, pull-based reactive stream processing with

This project is a technical study and analysis guide focused on the internal architecture of Node.js. It provides an in-depth examination of the runtime, focusing on how the engine manages memory handles, executes asynchronous operations, and implements core module logic. The guide specifically analyzes the integration of native C++ classes and functions into JavaScript and documents the behavior of the libuv event loop. It includes detailed references for optimizing performance by identifying V8 compiler bailouts and profiling execution to improve resource efficiency. The material covers a

Gevent is a Python coroutine concurrency library and asynchronous task manager designed for high-concurrency I/O tasks. It provides a cooperative networking framework for building asynchronous TCP, UDP, and HTTP servers, as well as a WSGI web server implementation for hosting web applications. The project is distinguished by its standard library monkey-patching tool, which replaces blocking synchronous functions with cooperative versions to enable asynchronous behavior in third-party code. This allows for a cooperative multitasking workflow where the system yields execution during I/O waits t

pysheeet is a technical reference library providing a curated collection of code snippets and implementation patterns for advanced Python development, system integration, and high-performance computing. It serves as a comprehensive guide for implementing low-level network programming, native C extensions, and asynchronous and concurrent programming. The project provides specialized frameworks for the development and deployment of large language models, including tools for distributed GPU inference and high-performance serving. It also includes detailed patterns for high-performance computing

This project is a technical programming guide and educational resource focused on Go internals, runtime mechanisms, and advanced language features. It provides detailed conceptual analysis of the language's execution model, including its scheduler, memory escape analysis, and garbage collection mechanisms. The material distinguishes itself through deep dives into high-concurrency system design, exploring the implementation of worker pools and communication channels. It also covers low-level network programming with a focus on I/O multiplexing and TCP state management, alongside a study of dis

This project is a C++ TCP server framework and educational socket programming guide. It provides a high-performance network library focused on event-driven architecture, implementing a reactor pattern to handle thousands of simultaneous client connections. The framework is distinguished by its multi-threaded event loop, which utilizes a main-sub reactor coordination model to distribute network events across a worker thread pool. It includes an abstraction layer for non-blocking socket I/O and event multiplexing via the epoll system call, decoupling network transport from application business

EventMachine is a reactor-pattern network framework for Ruby that provides an asynchronous I/O library for performing non-blocking network and file operations. It functions as a network server framework used to build scalable TCP and UDP servers and clients that process multiple simultaneous requests. The framework implements a concurrency model that dispatches network events to registered handlers using a single-threaded event loop. This approach allows for the management of high-concurrency network connections without the overhead of multi-threaded programming. The library covers the devel

Handy is a C++11 network server framework and event-driven networking engine designed for building high-performance concurrent TCP and UDP servers. It functions as an asynchronous I/O library and an HTTP server implementation that separates asynchronous network I/O from synchronous business logic to simplify server development. The framework distinguishes itself by utilizing platform-specific event notifications to manage millions of simultaneous network connections and providing an SSL/TLS network wrapper for encrypted asynchronous data transmission. It implements a half-sync/half-async proc

Kotlinx.coroutines is a library for managing non-blocking background tasks and structured concurrency within the Kotlin programming language. It provides a framework for executing concurrent operations and synchronizing shared state, replacing traditional thread management and complex callback chains with lightweight primitives. The library utilizes a structured concurrency hierarchy to organize hierarchical background tasks, ensuring that lifecycle management, cancellation, and timeout handling propagate automatically to prevent resource leaks. It employs continuation-passing style transform

Muduo is a C++11 event-driven network library and framework designed for building high-concurrency Linux servers. It provides a toolkit for implementing scalable network services and socket communication using non-blocking I/O and asynchronous event processing. The framework implements a multi-threaded TCP server architecture that distributes connection handling across multiple CPU threads to maximize server throughput. This is achieved through a one-loop-per-thread model and a reactor pattern implementation, which dispatch network events from a central demultiplexer to registered handler fun

Kore is an event-driven web and WebSocket server framework designed for building high-performance web services and APIs in C or Python. It functions as a secure, concurrent application framework that utilizes non-blocking I/O and isolated worker processes to handle high-concurrency traffic. The project is distinguished by a security-first architecture that features OS-level process sandboxing, privilege separation, and the isolation of private encryption keys into dedicated processes. It enables zero-downtime deployments through dynamic module hot-reloading and provides automated TLS certific

libwebsockets is an event-driven networking framework written in C. It provides a suite of tools for implementing HTTP servers and clients, WebSocket bidirectional communication, MQTT client messaging, and TLS-enabled socket encryption. The project distinguishes itself through a non-blocking event-loop architecture capable of scaling to high connection volumes by distributing network sessions across multiple service threads. It uses a protocol-based callback system and a pluggable event loop integration that allows the networking core to synchronize with external system event libraries. The

Luvit is an event-driven runtime for Lua that integrates libuv to provide non-blocking I/O and asynchronous system operations. It functions as an asynchronous network framework and execution environment that leverages Just-In-Time compilation for high-performance script processing. The platform enables the distribution of network traffic across multiple CPU cores through a TCP cluster manager that shares socket handles among child processes. It provides specialized capabilities for building HTTP servers by decoding incoming request streams and encoding responses via a stream processor. The r

CppGuide is a curated collection of educational resources and practical guides focused on C++ server development, Linux kernel internals, concurrent programming, network protocols, and security exploitation. It provides structured learning paths for backend developers, covering everything from interview preparation to building high-performance network servers and understanding operating system fundamentals. The guide distinguishes itself by offering in-depth, hands-on tutorials that walk through real-world implementations, including building a Redis-like server from scratch, designing custom

Vert.x is a reactive polyglot framework and asynchronous programming library for the Java Virtual Machine. It functions as an event-driven networking framework and toolkit for building non-blocking applications. The system enables the development of high-concurrency network services and event-driven microservices. It supports the creation of reactive services using multiple languages running on the JVM. The framework covers a wide range of capabilities including the management of HTTP and TCP network protocols, non-blocking file system access, and the integration of reactive clients.

async-std is a Rust asynchronous runtime and non-blocking I/O library. It serves as an asynchronous standard library, providing a set of alternatives to the core Rust library for managing concurrent tasks, networking, and file system access. The project implements a standard-library-mirrored API, offering asynchronous versions of existing synchronous types to maintain a familiar interface. This approach allows for asynchronous Rust development using an interface that reflects the ergonomics of the language's standard library. The runtime includes a task executor for scheduling and executing

Asio is a C++ library for performing network and low-level I/O operations using a consistent asynchronous model that avoids blocking program execution. It provides a portable, cross-platform interface for network socket communication across different operating systems, and manages multiple asynchronous operations without requiring explicit thread management or locking. The library implements a proactor-based asynchronous model where operations post completion handlers to a queue for later execution, and wraps operating system I/O multiplexing mechanisms like epoll, kqueue, IOCP, and select in

Hertz is a high-performance Go HTTP framework designed for building scalable microservices, RESTful APIs, and AI applications. It functions as a high-performance web server and a communication framework for microservices, utilizing non-blocking I/O and zero-copy memory management to handle high-concurrency traffic. The project distinguishes itself through a microservices communication toolkit that supports high-efficiency remote procedure calls via gRPC and Thrift protocols. It implements an asynchronous middleware engine based on an onion model, allowing for a pluggable request-response pipe

libco is a C++ coroutine library and user-space task orchestrator designed for cooperative multitasking and high-concurrency execution. It functions as a high-concurrency network framework and a synchronous-to-asynchronous wrapper that allows blocking system calls and socket functions to run asynchronously without modifying existing business logic. The project utilizes a specialized stack-copying context switching model to support millions of simultaneous TCP connections on a single machine. It includes a high-performance time wheel scheduler for managing asynchronous background jobs and dela

This project is a comprehensive educational resource and programming course covering C++ language semantics and features from C++03 through C++26. It provides structured tutorials and technical guides focused on modern C++ development. The material offers specialized instruction on template metaprogramming, including the use of type traits and compile-time computations. It features detailed guides on concurrency and parallelism for multi-core execution, as well as a reference for software design applying SOLID principles and RAII. Additionally, it covers build performance optimization to redu

Octane is a PHP application server accelerator and process manager that boots an application into memory to eliminate the startup overhead associated with each individual request. It functions as a runtime bridge for high-concurrency engines such as Swoole and RoadRunner, utilizing persistent worker processes to handle incoming HTTP requests. The project includes an in-memory application state manager that uses atomic tables to share data across workers and a concurrent task runner that executes multiple operations in parallel to reduce total request latency. It also manages worker lifecycles

This project is an instructional repository and learning resource providing a comprehensive collection of study notes, programming guides, and runnable source code examples. It serves as a guide for Java SE and Java web development, featuring a library of code samples that demonstrate common algorithms and technical implementations. The repository focuses on language core and runtime analysis, with detailed tutorials on multithreading and concurrency. It provides practical implementations of software architecture and design patterns, such as the singleton and strategy patterns, as well as exp

The MongoDB Python Driver is a client library and NoSQL database client used to execute CRUD operations and manage data within MongoDB databases using the Python programming language. It serves as a database connectivity library that handles authentication and connection pooling, while also providing a vector search client for managing embedding indexes and retrieving data based on semantic similarity. The driver supports both synchronous and asynchronous database driver models to perform non-blocking I/O operations and stream data from database clusters. It distinguishes itself through speci