I'm sorry if this is a duplicate, but I have yet to find a solution for this specific scenario.
We have a Rails application where most forms use a regular form submission. However, we also have forms that contain only one element, a checkbox. We are optimising our site for mobile use and thinking about making small forms, such as the one below, Ajax based. Note that the form below might have more than one row.
Will it confuse the user if larger forms require manual submission and smaller ones like this one submit automatically (using Ajax)? As you can see, we provide a message with a lifetime of 1000ms that indicates if the action produced a success or error.