Passing variables from user task to service task synchronous workflow

hello everyone,
i am new to camunda BPMN , i am building a workflow where user clicks on a button to trigger a registration workflow , the first step of the workflow is a form where user inputs his/her details after submitting the form we hit the camunda submit form Rest api, after the submission the next step is a service task which uses connector to send the information send from user task to a node.js api where perform validations and create user if validation passes else we throw the error.

my problems are →
1.) i can not pass values from my user task to the service task without using async before/after ,
2.) error thrown from node.js api is not caught in the camunda workflow even after using error boundary event.
i am really stuck any help would be really appreciated
i am attaching my workflow file please look and correct me if i am wrong anywhere
registeration-workflow.bpmn (14.2 KB)

Hey @shivam-chouhan ,

is there a specific reason, why you are using Connectors to implement the service task? If you want to run some node.js in the service task, the better option would be to implement the service task as external task. Camunda offers a JS external task client.
In that JS code you can then also throw a BPMN error that can be caught in the bpmn model. If you want to throw a bpmn error you have to specify the name of the error, when you throw it in your code as well.
If you use external task for your implementation you don’t need to take care about async. before and after as external task are asynchronous. Which is necessary in order to catch an error that comes from external.

I hope that helps