Triggering Updates on Records
Whether you’re trying to fire workflows or update time/date stamps for integration, you need to be careful how the related records may cause the parent/child records to update.
To update parent records you can use rollup summaries but keep in mind that updating the criteria of rollup summaries won’t trigger an update to last modified dates. To update child records you would need to use process builder.
A popular use case for integration would be to update the child contacts of an account when the account reaches integration criteria. Otherwise an account may be picked up by integration but its contacts wouldn’t.