Check to do post call using informatica cloud ReST API, you can dump data to flatfile and from flatfile move it over to DB, you can create 2 tasks and put it to task flow
This can be easily done in a single job with help of Informatica Cloud ReST V2 connector.
Advantages with ReST V2 Connector over ReST Connector:
1. You can use REST V2 Connector as a midstream transformation in a mapping to pass a single or multiple requests to a web service application and process the response data.
2. You can also pass data obtained from multiple transformations in the mapping pipeline and process the data
For more info refer the user guide HERE