# Global Architecture

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Cohort360 is divided in two parts:

1. The [front-end](https://github.com/aphp/Cohort360) web interface, developed with [React](https://fr.reactjs.org/)
2. The [back-end](https://github.com/aphp/Cohort360-Back-end) API, developed with [Django](https://www.djangoproject.com/) and [DRF](https://www.django-rest-framework.org/)

Cohort360 needs at least the following to operate:

* A SQL database (compatible with Django, see [here](https://docs.djangoproject.com/en/dev/ref/databases/))
* \[Optional] A celery backend, we recommand Redis (see [here](https://docs.celeryproject.org/en/stable/userguide/configuration.html))
* Configuring the front-end and back-end to match your needs, see the following pages:
  * [Django Back-end](/technical-documentation/django-back-end.md) 
  * [Front-ends](/technical-documentation/front-ends.md)

Cohort360 needs 2 other endpoints to fully operate:

* OpenID Connect (OIDC)
* An **HL7 FHIR API** exposing health records
* A **Query Executor API** that handles Cohort360's possibly complex queries to generate cohorts of patients. Without this API, Cohort360 will only be a data visualization interface and won't be able to execute complex queries.

![Architecture of the dependencies of Cohort360](/files/-MeiWH2sfCUyJLfdkx3E)

#### How it works?

The **front-end** should be able to:

* Get an authentication token (JWT) from an API using login form username and password, and use this token to talk to other APIs such as the Django back-end, the FHIR API, the QueryServer... This authentication method can be replaced easily if needed. OpenID connect is another option under development.
* Connect to a FHIR API to read medical data, Cohort360 does not write data to FHIR for now.
* Connect to a QueryServer API, or alternative, to execute complex queries and create Cohorts of patients that are then made available in the FHIR API.

The **back-end** should be able to:

* Connect and store application data (not medical data) in a Postgres database, Django is also compatible with other [RDBMS](https://docs.djangoproject.com/en/dev/ref/databases/) but we do not test it.
* Connect to the QueryServer to run complex queries, the back-end expose them to the front-end asynchronously.


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