We have a DevOps team which includes a BA, .NET developers and SAP developers. The .NET and SAP developers can and will only work on their particular discipline.
Some of our stories involve only .NET work; These are easy to write. Likewise for the SAP stories.
Some work involves effort which spans right from the user interface (.NET) down to the data store (SAP).
When a latter story is encountered, is the best practice to have one story with discipline-specific tasks (on the basis that a story should be a full vertical slice) or two separate stories (on the basis that each piece is independently worked on)?
The complexity here is that we can't rely on one of each developer being available to work on the story at the same time; Since those two tasks must be done as separate efforts of work (no matter how inter-dependent) it would seem unreasonable/unwise (in this case) to block the whole story because of one task being unable to be completed. (We could forever be waiting for both developers to become available. It is this race condition we want to avoid.)