One of our apps was written by one of those spaguetti coders who was always working on his own. As this falls into the 'technical debt' backlog, I am proposing the team (I am the team leader) a user story 'Redesign and create database and related store procedures etc.'). This user story obviously involves several tasks: design a database, create a database, create tables, create store procedures, create jobs. This is something that I think should be work by two people. Would you split this user story in two? Or just keep this one with several tasks on it?
First - it's not really a user story. Let's call it simply a task. Whether to allow more than 1 developer to work on it - yes. In modern approaches (JiT, ToC) it's more important to finish each task faster rather than have a lot of tasks in progress.
As for whether to split the task for each developer or not.. What's important is:
- People understand who's doing what
- It's easy to navigate between the full picture and the details
- It's SMART
I've seen both approaches work fine. But personally I think the tasks should be split if they can be delivered separately. Otherwise it's the same task regardless of how many people will work on it. From this POV it should be 1 task in your situation.
You can ask the team on what's more convenient for them. You can also give both options a try and then decide. But preferably don't complicate things if there's no necessity. So start simple.