==============
Backend Basics
==============

.. image:: /images/overview_architecture_diagram.png

The AcceleratXR backend platform utilizes a `micro-services <https://en.wikipedia.org/wiki/Microservices>`_ based architecture
composed of more than two dozen unique services. Each of these services provides a singularly focused set of functionality within
the platform. Functionality such as user account management (`acount-services <https://gitlab.com/AcceleratXR/Core/account_services>`_),
player achievements (`achievement-services <https://gitlab.com/AcceleratXR/Core/achievements_services>`_), virtual
economy (`economy-services <https://gitlab.com/AcceleratXR/Core/economy_services>`_), matchmaking
(`matchmaking-services <https://gitlab.com/AcceleratXR/Core/matchmaking_services>`_) and more.

True to micro-service principles each service within the platform maintains strict database access isolation and uses
a post/push methodology for performing write operations and delivering changes. As a result, no two services will have
access to the same database content. All write operations must be performed through a service's REST API. Data changes
are then distributed either via REST API polling or via push messaging. Push data is sent to other services via a common
messaging bus such as `redis <https://redis.io/>`_ while clients can optionally register for notifications to be
delivered via a secured `websocket <https://en.wikipedia.org/wiki/WebSocket>`_ connection.

Authentication is managed using a distributed `JSON Web Token <https://jwt.io/>`_ with each service having the capability to
decode and verify any given access token. The JWT access token contains all relevant information for a service to be
able to perform work on behalf of a given user including any relevant permissions and roles.

While the platform can be deployed using a variety of different methods `Kubernetes <https://kubernetes.io/>`_ has been
selected as the preferred orchestration system due to its powerful features, simplicity and ability to run in virtually
any environment.

In order to provide a unified set of endpoints for communicating with the platform `nginx <https://www.nginx.com/>`_ is
utilized as the primary load balancer and reverse proxy for all of AcceleratXR's backend services.

Lastly, the `Prometheus <https://prometheus.io/>`_ server is leveraged for gathering real-time statistics as well as
providing Kubernetes with the necessary metrics for performing automatic scaling of individual services.