pushpin.org

What It Is

Pushpin is a reverse proxy server “designed for realtime APIs.” It sits between clients and backend services, keeps client connections open, and lets the backend control realtime communication features such as HTTP streaming, HTTP long-polling, Server-Sent Events, and WebSocket. It is not a traditional message queue and does not persist data; it is more like a realtime API gateway.

Core Capabilities

Its biggest strength is that it is transparent to clients: clients continue communicating according to your API contract, while Pushpin remains a server-side implementation detail. The backend declares subscriptions through response headers such as Grip-Hold and Grip-Channel, or via WebSocket control messages, then publishes data through the HTTP control API on the default port 5561 or via ZeroMQ input. The backend can use any language or framework, and the documentation includes examples for Python/Django, Ruby, PHP, Node.js, and more. Pushpin itself is written in Rust and C++, and supports binary data, message deduplication, keep-alives, disconnect events, proxy chaining, and message queue integration.

Deployment, Open Source, and Pricing

The project is released under the Apache License 2.0, with source code available on GitHub, and supports self-hosting. The documentation states that it can run on Linux and macOS, with installation options for Debian/Ubuntu, RHEL-8-compatible distributions, Homebrew, Docker, and source builds. In terms of pricing, the project itself is free to use. Commercial support is provided by Fastly, but the documentation does not disclose pricing or SLA details.

Pros and Cons

The advantages are its low architectural intrusion, language-agnostic design, ability to reuse existing API authentication, logging, rate limiting, and analytics systems, and a clear horizontal scaling model: instances do not need to communicate with each other, and sticky sessions are not required. It is well suited to microservices, where each service can have its own Pushpin instance. The downside is that the abstraction level is relatively low: teams need to understand proxies, publish/subscribe, GRIP instructions, and control APIs. It also does not handle message persistence, so high-traffic scenarios often need to be paired with ZeroMQ, Kafka, RabbitMQ, or a custom messaging layer.

Who It’s For and Access from China

Pushpin is suitable for engineering teams that already have REST/API services and want to add SSE, WebSocket, or long-polling capabilities without rewriting the backend or being tied to a specific client SDK. For teams that simply want to build a frontend realtime application quickly, Socket.io or a hosted realtime service may be easier. The source text provides no information about access from China, so the availability of the domain, GitHub, and package repositories needs to be tested in practice. If access is unstable, alternatives such as Centrifugo, Socket.io, or a self-hosted Nginx/WebSocket gateway may be worth evaluating.