• Is there something forcing us to upgrade? e.g. unsupported gems for 4.2
• Do we gain any significant benefits from the upgrade at this point? e.g. faster ActiveRecord, smaller memory footprint, less objects in memory, etc.

Bare in mind that we don't have a staging environment. We need to test this in staging, with staging workers, webhooks, database etc. It seems like an opportunity to set this up.

• We gain access to the ActionController::API, so that our API has no unecessary middleware(e.g. SessionMiddleware). This might make the API faster
• We gain access to the ActionCable which might be a solution for live updates - We have to figure out if it is worth it.
• We now have cleaner syntax for controller tests(E.g. instead of post :create, {id: 2} we have the more explicit post :create, params: {id: 3}.
• We gain access to the redirect_back helper that has a fallback location when the referrer doesn't exist

Apart from that, there is nothing that forces us to upgrade