old_contents: from django.db import models
  from django.db.models.signals import post_save, post_delete
  
  from wagtail.wagtailcore.models import Page
  
  from wagtail.contrib.wagtailfrontendcache.utils import purge_page_from_cache
  
  
  def post_save_signal_handler(instance, **kwargs):
      purge_page_from_cache(instance)
  
  
  def post_delete_signal_handler(instance, **kwargs):
      purge_page_from_cache(instance)
  
  
  def register_signal_handlers():
      # Get list of models that are page types
      indexed_models = [model for model in models.get_models() if issubclass(model, Page)]
  
      # Loop through list and register signal handlers for each one
      for model in indexed_models:
          post_save.connect(post_save_signal_handler, sender=model)
          post_delete.connect(post_delete_signal_handler, sender=model)
  
new_contents: from django.db import models
  from django.db.models.signals import post_delete
  
  from wagtail.wagtailcore.models import Page
  from wagtail.wagtailcore.signals import page_published
  
  from wagtail.contrib.wagtailfrontendcache.utils import purge_page_from_cache
  
  
  def page_published_signal_handler(instance, **kwargs):
      purge_page_from_cache(instance)
  
  
  def post_delete_signal_handler(instance, **kwargs):
      purge_page_from_cache(instance)
  
  
  def register_signal_handlers():
      # Get list of models that are page types
      indexed_models = [model for model in models.get_models() if issubclass(model, Page)]
  
      # Loop through list and register signal handlers for each one
      for model in indexed_models:
          page_published.connect(page_published_signal_handler, sender=model)
          post_delete.connect(post_delete_signal_handler, sender=model)
  
subject: Use page_published signal for cache invalidation instead of post_save