Trigering post_save signal only after transaction has completed

I think the simplest way is to use transaction.on_commit(). Here’s an example using the models.Model subclass Photo that will only talk to Elasticsearch once the current transaction is over:

from django.db import transaction
from django.db.models.signals import post_save

@receiver(post_save, sender=Photo)
def save_photo(**kwargs):
    transaction.on_commit(lambda: talk_to_elasticsearch(kwargs['instance']))

Note that if the transaction.on_commit() gets executed while not in an active transaction, it will run right away.