There are two main methods:

HTTP_GetFireAndForget

HTTP_PostFireAndForget

The "Get" method runs http get requests and the "Post" method runs post requests.

Implementation Guide for Fire-And-Forget standard processes in OutSystems:

1. Create a REST api with Get or Post method and your custom parameters. You may set the API with the HTTP Security as "None" and Internal Access Only if you would like to call as "https://localhost" in the requests;

2. Implement your asynchronous logic in the API method;

3. Use the above methods Fire-And-Forget to trigger your process with a custom Timeout.

Note: With this implementation you may not have control over the Job request running asynchronous in the IIS server, so be careful with your implementation. If you would like to create a cancel option, you may create a control entity or use a custom Site Property for this purpose.