def delete_expired(self, expires):
    """Delete all expired results."""
    with transaction.atomic(using=self.db):
        raw_delete(queryset=self.get_all_expired(expires))

import random

from django.conf import settings


class CustomRouter:
    def db_for_read(self, model, **hints):
        """
        Return either default or one of the replicas
        """

        db_read = [
            "default",
        ]

        if settings.REPLICA1_URL is not None:
            db_read.append("replica1")
        if settings.REPLICA2_URL is not None:
            db_read.append("replica2")

        return random.choice(db_read)

    def db_for_write(self, model, **hints):
        # Always return the default database
        return "default"

    def allow_relation(self, obj1, obj2, **hints):
        return True

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        return True