I understand that there are many ways to design a solution. When we should use a

Another aspect to watch out for is when launching many sub-processes at a time from with in a parent process. As the Sub-Process instances start on the same execution engine as the parent, you might want to reduce the load on same engine by launching these sub-processes via sending messages instead of using sub-process node. Below documentation section contains some information on how to do it. One highlight from this section is "Avoid using sub-process activities to start processes based on query rules when each new item in a data store starts a new process. Use process-to-process messaging instead."

forum.appian.com/.../Messaging_Best_Practices.html

Another aspect to watch out for is when launching many sub-processes at a time from with in a parent process. As the Sub-Process instances start on the same execution engine as the parent, you might want to reduce the load on same engine by launching these sub-processes via sending messages instead of using sub-process node. Below documentation section contains some information on how to do it. One highlight from this section is "Avoid using sub-process activities to start processes based on query rules when each new item in a data store starts a new process. Use process-to-process messaging instead."

forum.appian.com/.../Messaging_Best_Practices.html