Seamlessly design your API schema with GraphQL Federation and implement your services with gRPC

Features • Demo • Getting Started • License

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✨ Features

• Schema-First GraphQL: Define your data contract in SDL and generate type-safe gRPC resolvers instantly
• gRPC Backends: Leverage gRPC's binary protocol for blazing-fast RPC with built-in codegen for go (More languages coming soon)
• API Bridging: Wrap legacy REST or SOAP services behind GraphQL types without rewriting existing backends
• End-to-End Type Safety: Maintain type integrity from schema to transport with auto-generated clients and servers

🚀 Demo

graph LR
  client["Clients (Web / Mobile / Server)"] --> routerCore["Router Core"]

      subgraph routerBox["Cosmo Router (API Gateway)"]
      routerCore
      plugin["✓ Users Service (Plugin)<br/>Implementation"]
      routerCore -->|gRPC| plugin
    end

  routerCore -->|HTTP| subA["Products Subgraph<br/>(GraphQL Server)"]

  plugin -->|HTTP| restA["External REST API"]

  %% Styling
  classDef pluginFill fill:#4a7c59,stroke:#2d5a3d,stroke-width:2px,color:#ffffff;
  classDef restFill fill:#c19a6b,stroke:#a0804f,stroke-width:1.5px,color:#ffffff;
  classDef routerFill fill:#5a8ea2,stroke:#3d6e80,stroke-width:1.5px,color:#ffffff;
  classDef subgraphFill fill:#8b6f47,stroke:#6d5637,stroke-width:1.5px,color:#ffffff;
  classDef clientFill fill:#e8dcc6,stroke:#d4c4a8,stroke-width:1.5px,color:#2d3436;
  class plugin pluginFill;
  class restA restFill;
  class routerCore routerFill;
  class subA subgraphFill;
  class client clientFill;

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This demo showcases a federated GraphQL architecture with two different implementation approaches:

• Users Subgraph: Implemented as a Go-based Router plugin (Cosmo Connect) running directly inside the Cosmo Router - no separate service needed
• Products Subgraph: Traditional standalone GraphQL server using Apollo Server (running on port 3011)
• Cosmo Router: Composes both subgraphs into a unified GraphQL API (running on port 3010)

The architecture demonstrates how Router plugins enable:

• Direct integration with external services (REST APIs, databases, gRPC services) through the plugin layer
• Embedded subgraphs with optimal performance by running inside the router process
• Seamless bridging between GraphQL and any backend protocol
• Traditional standalone subgraphs (Products) for compatibility with existing systems

🛠️ Getting Started

Prerequisites

• Linux or macOS
• Node.js LTS
• npm or yarn

Installation

1. Clone the repository:

   git clone https://github.com/wundergraph/cosmo-plugin-demo.git
   cd cosmo-plugin-demo

2. Install dependencies:

   npm install

3. Build the plugin, start the router and the subgraphs:

   npm start

4. Open the GraphQL Playground at http://localhost:3010 and run the following query:

   query {
     users {
       id
       name
       email
       role
       products {
         id
         name
         price
         description
       }
     }
   }

📝 License

This project is licensed under the Apache License 2.0. See the LICENSE file for details.

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