Looking at some samples of the phrases "during the backend" and "over the backend" on Google Publications, it appears that evidently just about anything that operates in the backend (procedures, services, etc. In many instances, the absolute path for each of the prepositions is usually easily inferred from the context, https://zanejfztl.onesmablog.com/5-essential-elements-for-front-end-development-agency-77195859