Need the ability to write the Marketo Custom Object information to Salesforce object

[Ben_Griffith1]

A much simpler approach would be to just create a web service in APEX and expose it publicly.  If you need to access Marketo through its API, store REST credentials in a custom setting in SFDC.

For Nikhil's example, this could be the one point where the custom object is created in the first place and SFDC record is too.  No intermediary systems.