Elasticsearch DSL for all null values between 2 timestamps

I have this structure JSON in elasticsearch. I am having trouble creating a DSL to search for all null values of awsKafkaTimestamp that are in between a post.timestamp range of A and B?

  "tracer": {
    "post": {"timestamp": 123123},
    "awsKafkaTimestamp": null,
    "qdcKafkaTimestamp": null

Have a look at https://www.elastic.co/guide/en/elasticsearch/guide/current/_dealing_with_null_values.html