Global variable in python application with potentially multiple instances

Question

I'm writing a Python/MongoDB/AWS Lambda application to store appointment info in a DB, with the option to have another appointment 'prioritized' over it (by using a key value called 'priority').

As part of the implementation, I have a function called get_next, which pulls the next open appointment from the DB and returns it (if no prioritized appointment) or the prioritized appointment if it exists.

def get_next(self, appointmentid= None):
    keydict = {
        'sessionid' : self.info['id'],
        'status' : 'open'
    }
    if appointmentid not in (None, ''):
        keydict.update({'appointmentid' : appointmentid })

    next_in_queue = self.db.getdetailsbykey("appointments", keydict, sortfield='_id', asc=False, suppressid=True)

    if 'priority' in next_in_queue and next_in_queue['priority'] not in ('', None):  
        priority = self.get_next(appointmentid=next_in_queue['priority'])
        if priority is not None:
            return priority
    return next_in_queue

Here getdetailsbykey is a wrapper around PyMongo's find_one:

def getdetailsbykey(self, collection_name, keydict, sortfield=None, asc=False, suppressid = True):
        #if 'dict' not in str(type(keydict)):
        if type(keydict) is not dict:
            return None
        #collection = self.db[collection_name]
        collection = self.db[collection_name].with_options(codec_options=CodecOptions(tz_aware=True, tzinfo=timezone))
        if sortfield is None:
            if suppressid:
                data = collection.find_one(keydict,  {'_id' : 0})
            else:
                data = collection.find_one(keydict)
        else:
            if asc is True:
                sortoption = 1
            else:
                sortoption = -1
            if suppressid:
                data = collection.find_one(keydict, {'_id' : 0}, sort=[(sortfield, sortoption)], )
            else:
                data = collection.find_one(keydict, sort=[(sortfield, sortoption)])
        return data

However, as is obvious, this is susceptible to a 'loop' issue if there is ever a circular arrangement of appointments in priority. Usually, I'd address this using a global variable but in this case I'm not so sure as this will be an application running on an AWS lambda instance, so my question is - will instances share the variable (and hence the value - which would be a Bad Thing(tm) ) ??

I would use a loop to do this instead of recursion, but I feel recursion is a better way to handle this as compared to a loop.

EDIT/UPDATE: The closest I have come to a solution is the following:

def get_next(self, appointmentid= None, ref_appt = None):
        keydict = {
            'sessionid' : self.info['id'],
            '$or' : [{ 'status' : 'open'}, { 'status' : 'inprogress'}]
        }
        if appointmentid not in (None, ''):  # if we have a specific id
            keydict.pop('$or', None)
            keydict.update({'id' : appointmentid })  # retrieve it

        next_in_queue = self.db.getdetailsbykey("appointments", keydict, sortfield='_id', asc=False, suppressid=True)
        if ref_appt is None:  # if this is the 0th level of recursion
            ref_appt = next_in_queue['id']  #save the id

        if next_in_queue is not None and 'priority' in next_in_queue and next_in_queue['priority'] not in ('', None):  # if there is a higher priority appointment
            priority = self.get_next(appointmentid=next_in_queue['priority'], ref_appt= ref_appt])
            if priority is not None:  # retrieve the appointment 
                if ref_appt != priority['id']:
                    return priority  # if there is a circular loop, this will not execute

        return next_in_queue

This should cause the last but one element in the loop to be returned, should a loop exist. However, my core question still stands - does the global variable in a python application with potentially multiple instances get shared across instances?

Any pointers/inputs would be very welcome.