Several anti-spam solutions exist on Drupal to prevent the submission of forms (contact, newsletter subscription, etc.) by more or less well-intentioned robots. Without wanting to be exhaustive, we can use the Honeypot and Antibot modules which provide (different) non-intrusive defence mechanisms, or the captcha / recaptcha modules which ask the visitor to respond to different challenges before allowing him to submit the form.
For some purposes it may be necessary to have content, or content elements, that may vary according to a certain time period, and therefore require a cache invalidation according to a certain duration. This is for example the typical case of a list of future and/or past events, which must invariably change over time.
Drupal 8 has three cache systems:
Until Drupal 8.7, we had a drush command that was very useful for developing content entities, and updating them as they evolved with the project. This command, drush entup or drush entity-updates, allowed us to update the definition of the entities and/or their fields.
For e-commerce sites offering training or events, an extremely interesting function is to offer visitors to subscribe to the training or event in question in order to be notified as soon as a new session, a new date, is available.