---
description: This article outlines how to use Aidbox Forms with external FHIR servers.
---

# External FHIR servers as a data backend

## Overview

Aidbox Forms module uses Aidbox's FHIR API capabilities to store all it's data. But sometimes it's appropriate to use other FHIR backends. Aidbox Forms provides a simple and granular way to specify external FHIR servers for data management.

## Data Domains

Data used by `Aidbox Forms` has different nature and can have different storage requirements and strategies.

We split data in 4 domains, and last 3 of them can have it's own FHIR backend:

> Because `system resources` are non FHIR resources - there is no FHIR backend configuration for them.

1. `System resources` - non-FHIR resources, used by `Aidbox Forms` for extended functionality.
2. `Content resources` - `Questionnaire` resource (the main focus and result of `Forms Builder`).
3. `Terminology resources` - `ValueSets` and `Concepts`.
4. `Production resources` - `QuestionnaireResponse` resource and other FHIR resources that contain PHI/Production data.

## Storage Defaults

By default all data is stored in Aidbox and there is no need for any configuration.

## Storage Configuration

Storage configuration lives in **default** `SDCConfig` resource. (read [more](configuration.md))

IMPORTANT: config should have `default: true` property set

### Storage Configuration structure

For every domain we have separate key:

* `form-store` - content resources domain
* `data-store` - production resources domain
* `term-server` - terminology resources domain

To enable external FHIR Backend we should specify next fields for it:

* `endpoint` - URI to FHIR API
* `headers` (optional) - Additional HTTP headers for requests (Authorization for example)

Example:

```yaml
[store-key]:
    endpoint: 'http://my-ehr.com/fhir'
    headers:
        Authorization: 'Basic cm9vdDpzZWNyZXQ='
```

#### Form Storage

Store `Questionnaire` resource only

> WARN: assembled forms and components are not yet supported with external storage.

```yaml
form-store:
    endpoint: "https://fhir-server.com/fhir"
```

#### Data Storage

Store `QuestionnaireResponse` and all FHIR Resources except `Questionnaire`.

This store will be used as source in `$populate` operations, and as target in `$extract`+`$process-response` operations

```yaml
data-store:
    endpoint: "https://fhir-server.com/fhir"
```

#### Terminology service

> `ValueSet` search and `ValueSet/$expand` operation

```yaml
term-service:
    endpoint: "https://fhir-server.com/fhir"
```

### Full config example:

```yaml
POST /SDCConfig
content-type: text/yaml

id: cfg-1
resourceType: SDCConfig
name: Config with external fhir servers
default: true
form-store: 
    endpoint: 'http://forms-repo.com'
data-store: 
    endpoint: 'http://my-ehr.com/fhir'
    headers:
        Authorization: 'Basic cm9vdDpzZWNyZXQ='
term-server:
    endpoint: 'http://tx.com/fhir'
```

### Multitenancy Support

* Default system `SDCCOnfig` (for `root` Organization) does not take effect on tenants
* Every tenant have their own default config and thus separate FHIR backends setup