If previous processes are not yet completed if you change existing CDT(Adding ad

An update to @Sikhivahans' post:
Passing expression rules and interfaces by Keyword is actually quite dangerous. This is because, if you call an expression rule or interface by not passing all parameters, the ones missed will be passed as null. In addition, this will NOT be caught by Appian, and could lead to Production defects.

Another option is to add a version to the interfaces and expression rules you are updating (such as V2), and have only the newest process models call the newest version of the interfaces, and therefore there is no issue of process instances failing due to changes to interfaces. The disadvantage to this techniqueis that any bugs identified in all versions of the interface require the bug fixes to be applied to all versions of the interfaces.

An update to @Sikhivahans' post:
Passing expression rules and interfaces by Keyword is actually quite dangerous. This is because, if you call an expression rule or interface by not passing all parameters, the ones missed will be passed as null. In addition, this will NOT be caught by Appian, and could lead to Production defects.

Another option is to add a version to the interfaces and expression rules you are updating (such as V2), and have only the newest process models call the newest version of the interfaces, and therefore there is no issue of process instances failing due to changes to interfaces. The disadvantage to this techniqueis that any bugs identified in all versions of the interface require the bug fixes to be applied to all versions of the interfaces.