Store data between a-sync calls

We use and need to store incoming data between two a-sync calls to a backend system. After the first call the backend calls back to a flow service. And at that moment I need the original incoming data. What method is everyone using for this? Is anyone using pub.Storage for this?
In rare situations there could be hours between the two calls but usualy seconds. And we might be in a cluster situation, who knows with webmethods.IO SaaS.

Thanks for replies.

What you want to achieve is straightforward in a workflow, a less in a flow service.
In a workflow you simply take the whole connector data structure and then do what you want with it (including sending it to a flow service.)
Since you’re talking about async calls, I see no problems in using workflows for your use cases - at least from what I read in your post.

What I had to mention was that we need the result of the first a-sync call before the second can be execute. Se execution has to be suspended until the call back. I don’t think a workflow can be paused until a call back is received or am i wrong?

A workflow cannot be paused. But it can be split into two workflows, each triggered by a webhook (your callbacks being treated as webhooks that trigger workflows in this case.)