From Content Services version 6.2 it is possible to create custom transforms that run in separate processes known as T-Engines (short for Transformer Engines). The same engines may be used in Community and Enterprise Editions. They may be directly connected to the Repository as Local Transforms, but in the Enterprise edition there is the option to include them as part of Alfresco Transform Service (ATS), which provides a more balanced throughput.
A T-Engine is intended to be run as a Docker image, but may also be run as a standalone process.
Prior to Content Services 6.0 Legacy transformers ran within the same JVM as the Repository. They and their supporting classes were deprecated in Content Services 6.0 and have now been removed. Content Services 6.2 still uses them if a rendition cannot be created by the Transform Service or Local Transforms. The process of migrating custom legacy transformers is described at the end of this page.
One of the advantages of Custom Transforms and Renditions in Content Services 6.2 and above is that there is no longer any need for custom Java code, Spring bean definitions, or alfresco properties to be applied to the Repository. Generally custom transforms and renditions can now be added to Docker deployments without having to create or apply an AMP/JAR, or even restarting the repository.