Skip to content


The "Relay API Gateway" is a framework for creating a REST API server for building applications and workflows on top of it. It abstracts away various backend systems, provides user management, authentication, caching, locking, authorization and a modular system for composing an API with so called API bundles. Various bundles are readily available and can be configured to your needs, or you can write your own bundles to extend the system/API.

flowchart TB style api_gateway stroke:#338555,color:#338555 ext_apps["External Desktop/Mobile/Server/Web Applications"] oidc_server["OpenID Connect Server (e.g. Keycloak)"] ext_service1["External Service A"] ext_service2["External Service B"] subgraph api_gateway["API Gateway"] api["API"] core_bundle["Core Bundle"] custom_bundle1["Bundle A"] custom_bundle2["Bundle B"] end api --> core_bundle api --> custom_bundle1 api --> custom_bundle2 custom_bundle1 --> ext_service1 custom_bundle2 --> ext_service2 ext_apps --> api_gateway ext_apps --> oidc_server core_bundle --> oidc_server

The framework consists of a core bundle which provides functionality that's useful in a multitude of API use cases, authentication, caching, logging, automatic API documentation, integration with the Symfony and API Platform frameworks etc.

All other functionality is implemented in extra bundles which can add new endpoints to the API and, in turn, can depend on other bundles and their endpoints. For example a bundle providing a library management API can add new endpoints for working with books by talking to an external library system. It can depend on the core bundle for user management and authentication.

API Clients

External apps, like browser or mobile applications can be written easily to access data via the API. The user authentication is done via an OIDC server like Keycloak.

An example for a web application would be the Library application.

External services like server applications that don't act on behalf of a user can access the API via "Client Credential" grants, also available in Keycloak for example.

Extending and Customizing

The API gateway can be easily extended by simply installing an existing bundle, changing exiting bundle behavior via event hooks, or writing your very own bundle.

If you write your own bundle you can create completely new APIs, or connect an existing API to a new external system. If you then share your bundle with the world everyone can install it and profit 😊

For how to write your own bundle please see our Developer Guide.