When should I be using a component interface?

The major reason why you should be using a CI is to reuse your business logic. You will be writing the business logic in a component. But when you are trying to insert data into the specific transaction tables outside of the component, then instead of writing the whole business logic and validations, you can easily use a CI to insert the data.

Also if you want to integrate your peoplesoft system with an external system, you can use CI. It will give three benefits. 1. Data Validations & Business logics are taken care. 2. No need to provide database access to the external application. 3. You can extend the security model existing in PeopleSoft.

If you need to insert/update/delete data through PeopleCode, and your PeopleCode will require replicating a lot of existing business logic that already exists in a component then a component interface is the best approach. Once you learn how to use them, they will be the fastest and most robust solution for such cases.

If you are performing simple changes, then using a CI becomes overkill as there is an overhead to using a CI on both the system and on development time. Similarly, large amounts of batch processing may be too much for a CI to handle or may be considerably slower using a CI.