def get_change_record(hostname: str, addr: str, rrtype: str):
    """Return a Route 53 request to UPSERT a resource record.

    As documented in
    https://boto3.amazonaws.com/v1/documentation/api/latest/reference/ \
        services/route53.html#Route53.Client.change_resource_record_sets
    """
    assert rrtype in ('A', 'AAAA')
    return {
        'Action': 'UPSERT',
        'ResourceRecordSet': {
            'Name': hostname,
            'Type': rrtype,
            'TTL': 60,
            'ResourceRecords': [{'Value': addr}]
        }
    }