> For the complete documentation index, see [llms.txt](https://chsakell.gitbook.io/harmony/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://chsakell.gitbook.io/harmony/configuration/dependencies/databases.md).

# Databases

Harmony uses the following database providers:

* **SQL Server** *(optional)*: <mark style="color:orange;">Harmony</mark> database is used to store project management tool's **domain entities** such as workspaces, boards and cards. It also stores the user entities used for authentication and authorization. \
  The only application that has a dependency to the Harmony database is the <mark style="color:blue;">**Harmony.Api**</mark>**.**\ <mark style="color:blue;">**Harmony.Notifications**</mark> & <mark style="color:blue;">**Harmony.Automations**</mark> services, use their own databases, *Harmony.Notifications.Jobs* & *Harmony.Automations.Jobs* respectively for HangFire jobs.&#x20;
* **PostgreSQL** *(optional):* Same as above. You can use either SQL Server or PostgreSQL for the core databases.
* **MongoDB Server**: MongoDB schema-less database named <mark style="color:orange;">harmony\_automation</mark> is used for implementing flexible automations. The database contains the available automation template & the per board automation configurations. The only application than can directly access the MongoDB database is the <mark style="color:blue;">**Harmony.Automations**</mark>.
* **Redis**: Harmony is a scalable system and one of its main features is that syncs all updates across all connected clients. In order to support this <mark style="color:blue;">**Harmony.SignalR**</mark>, the web application responsible to read messages from RabbitMQ and push them to all connected clients via WebSocket, uses [Redis Backplane](https://learn.microsoft.com/en-us/aspnet/core/signalr/redis-backplane?view=aspnetcore-8.0) for scaling out.

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[SQL Server](/harmony/configuration/dependencies/databases/sql-server.md)
{% endcontent-ref %}

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[PostgreSQL](/harmony/configuration/dependencies/databases/postgresql.md)
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[MongoDB Server](/harmony/configuration/dependencies/databases/mongodb-server.md)
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[Redis](/harmony/configuration/dependencies/databases/redis.md)
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