---
title: "Message Bus"
slug: "message-bus"
abstract: "Overview of Sitecore Message Bus supported infrastructure, references, scaling, and privacy and security."
---
# Message Bus

The Message Bus role runs on [Rebus](https://github.com/rebus-org/Rebus) and is a message transport mechanism which allows application roles to communicate across boundaries.

## Supported infrastructure

You can host the Message Bus role on:

- SQL Server
- SQL Azure
- Azure Service Bus

> [!note]
> If you are upgrading from Sitecore 9.1 to 9.2, Sitecore does not provide a tool for migrating from SQL to Azure Service Bus.

Refer to the [Sitecore compatibility table](https://kb.sitecore.net/articles/087164) for compatible versions.

## Reference structure

The Message Bus role has its place in the Sitecore reference structure. It can be referenced by other roles, and it can also reference other roles.

![Illustration showing the Message Bus role's place in the Sitecore reference structure.](https://doc.sitecore.com/api/markdown-image/xp/en/developers/100/platform-administration-and-architecture/images/message-bus.png)

### Referenced by

The Message Bus role is referenced by the following roles:

- [Content Delivery](https://doc.sitecore.com/xp/en/developers/100/platform-administration-and-architecture/content-delivery--cd-.html "Content Delivery (CD)")
- [Content Management](https://doc.sitecore.com/xp/en/developers/100/platform-administration-and-architecture/content-management--cm-.html "Content Management (CM)")
- [EXM Dispatch](https://doc.sitecore.com/xp/en/developers/100/platform-administration-and-architecture/exm-dispatch.html "EXM Dispatch")
- [Marketing Automation Engine](https://doc.sitecore.com/xp/en/developers/100/platform-administration-and-architecture/marketing-automation-engine.html "Marketing Automation Engine")
- [Marketing Automation Operations service](https://doc.sitecore.com/xp/en/developers/100/platform-administration-and-architecture/marketing-automation-operations-service.html "Marketing Automation Operations service")
- [xConnect Collection service](https://doc.sitecore.com/xp/en/developers/100/platform-administration-and-architecture/xconnect-collection-service.html "xConnect Collection service")
- [xConnect Collection Search service](https://doc.sitecore.com/xp/en/developers/100/platform-administration-and-architecture/xconnect-collection-search-service.html "xConnect Collection Search service")
- [Sitecore Cortex™ Processing Engine](https://doc.sitecore.com/xp/en/developers/100/platform-administration-and-architecture/sitecore-cortex-processing-engine.html "Sitecore Cortex Processing Engine")

### References

The Message Bus role does not reference other roles.

## Privacy and security

The Message Bus role does not handle personal data by default and privacy concerns are described by the referencing roles.