Benchmarked at one million concurrent WebSocket connections and 30 million delivered messages per minute on a single server, Centrifugo is a self-hosted real-time messaging server that integrates with any backend language — Node.js, Python, Go, Ruby, PHP, Java — without requiring architectural changes to your existing application. It handles persistent connections over WebSocket, HTTP-streaming, Server-Sent Events, gRPC, and experimental WebTransport, routing messages through a channel-based PUB/SUB model with automatic reconnection recovery that replays missed messages from hot channel history. Built-in horizontal scaling operates through Redis (including Redis Cluster, AWS ElastiCache, Valkey, KeyDB, and DragonflyDB), NATS, or PostgreSQL brokers, allowing multi-node deployments without external message queues. The server provides JWT-based authentication using HMAC or RSA keys, granular channel permissions, online presence tracking showing who is currently subscribed to a channel, and an RPC proxy that forwards client calls to your backend over HTTP or gRPC. The embedded ReactJS admin web interface displays real-time connection statistics, node information, and provides an interactive API console for publishing messages, managing subscriptions, and inspecting channel history. Official client SDKs are available for JavaScript, Dart, Go, Swift, and Java, with unidirectional transports requiring no SDK at all. Centrifugo also supports delta updates to minimize bandwidth, connection event proxying, and Prometheus-compatible metrics for Grafana monitoring. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache 2.0 licensed.

Stateful serverless actors that run indefinitely, sleep when idle, and persist state across restarts without external database round trips. Rivet provides a vendor-neutral alternative to Cloudflare Durable Objects, delivering long-running processes with co-located in-memory state and per-actor SQLite databases on any infrastructure you choose. The Rust engine comprises four packages: Pegboard for actor orchestration, Gasoline for durable execution, Guard for traffic routing via Envoy, and Epoxy implementing multi-region KV storage through EPaxos consensus. Each actor maintains instant-access in-memory state plus a dedicated SQLite database for relational queries, backed by RocksDB on single nodes or PostgreSQL with NATS pub/sub for multi-node clusters. RivetKit SDKs in TypeScript, Rust, and Python support built-in WebSocket connections, task queues, scheduling, and CRDT-based real-time collaboration. The v2.3 rewrite moved the core runtime from JavaScript to native Rust via WebAssembly, eliminating main-thread blocking across Node.js, Bun, Deno, and Cloudflare Workers. A built-in dashboard provides actor inspection with real-time Prometheus metrics. Deploys as a single Docker container on port 6420 with optional PostgreSQL for persistence. Available on RepoCloud with a dedicated VPS under the Apache 2.0 license.

Backed by nearly 80,000 GitHub stars and recognized as one of the most popular developer tools in the open-source ecosystem, Hoppscotch delivers a complete API development platform that runs instantly in any browser with zero installation. The platform supports six protocols out of the box including REST with full HTTP method coverage, GraphQL with schema introspection and multi-column documentation, WebSocket for full-duplex communication, Socket.IO, MQTT for IoT messaging, and Server-Sent Events for real-time streaming. Request collections organize your API calls into logical groups with support for sub-folders, environment variables with scope inheritance, pre-request scripts and post-request test scripts written in JavaScript, and automatic code snippet generation in over twenty languages and frameworks. Teams can collaborate in real-time with shared workspaces, role-based access controls, and cloud synchronization across devices. Migration from Postman, Insomnia, or OpenAPI specifications happens with a single click import. The self-hosted edition deploys via Docker Compose with PostgreSQL for data persistence, supporting SSO authentication through SAML and OAuth providers, SMTP configuration with OAuth2, and admin dashboard for user management. The platform also ships as a native desktop application for macOS, Windows, and Linux with offline support, plus a CLI tool for running collections in CI/CD pipelines. A built-in proxy mode bypasses CORS restrictions during development, and an interceptor enables request debugging and response modification. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.