Slow bool query

Elastic Stack Elasticsearch
1

The following request takes at least 500ms every time we execute it. This is on a an index with 5 primary shards of 1.2GB each. Is there anything in the query that would explain the slowness ? The cluster is otherwise performant. We're still running ES 2.4.1.

{
  "query": {
    "filtered": {
      "filter": {
        "bool": {
          "must": [
            {
              "has_parent": {
                "type": "article",
                "filter": {
                  "bool": {
                    "must": [
                      {
                        "term": {
                          "account_id": 67316
                        }
                      },
                      {
                        "term": {
                          "brand_id": 3600001925
                        }
                      },
                      {
                        "terms": {
                          "section_id": [
                            200923332,
                            3600117465
                          ]
                        }
                      }
                    ],
                    "must_not": []
                  }
                }
              }
            },
            {
              "term": {
                "is_active": true
              }
            },
            {
              "terms": {
                "status": [
                  "draft",
                  "published"
                ]
              }
            },
            {
              "terms": {
                "is_source": [
                  true
                ]
              }
            }
          ],
          "must_not": []
        }
      },
      "query": {
        "multi_match": {
          "fields": [
            "body*^1.5",
            "title*^2"
          ],
          "query": "",
          "type": "phrase_prefix",
          "zero_terms_query": "all"
        }
      }
    }
  },
  "sort": {
    "updated.timestamp": {
      "nested_path": "updated",
      "order": "desc"
    }
  }
}
2

Parent/Child + Nested fields (sort) are most likely the ones I'd think about.

3

I remember seeing similar problem with the project that I am working on.
Initially, we were using parent-child documents where the search response times are way higher. We migrated to nested structure and noticed considerable change in the search response times.