Analytics

Drupal has long had a variety of access control modules, to make it so you can easily control who can view or edit particular pages. There are actually several different layers of APIs to control this in Drupal core -- the modules generally provide a user interface to let you control access by content type, by tagging content with particular terms, through their position on a menu, or through a group. The Field Permissions module lets you control access to particular fields on an entity.

One of our clients has a custom surveying application built with a Drupal back end, and a VueJS/headless front end. They use this application to record observations in various buildings and sites that don't meet accessibility requirements.

They give their clients access to the front end. This application organizes observations into particular sites, in particular projects, grouped by the requirement. Each observation can have photos attached, along with notes and recommended solutions.

Sometimes a simple reminder can spur a sale. If you have repeat customers that log into your commerce site, you may be able to remind them if they did not complete a checkout.