SELECT 
  cscart_product_reviews.*, 
  cscart_users.company_id as reply_company_id, 
  cscart_companies.company as reply_company, 
  cscart_country_descriptions.country as country 
FROM 
  cscart_product_reviews 
  LEFT JOIN cscart_users ON cscart_product_reviews.reply_user_id = cscart_users.user_id 
  LEFT JOIN cscart_companies ON cscart_users.company_id = cscart_companies.company_id 
  LEFT JOIN cscart_country_descriptions ON cscart_product_reviews.country_code = cscart_country_descriptions.code 
  AND cscart_country_descriptions.lang_code = 'en' 
WHERE 
  1 
  AND cscart_product_reviews.product_id IN (6876) 
  AND cscart_product_reviews.status = 'A' 
ORDER BY 
  cscart_product_reviews.helpfulness desc 
LIMIT 
  0, 10

Query time 0.00061

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "5.94"
    },
    "ordering_operation": {
      "using_filesort": true,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_product_reviews",
            "access_type": "ref",
            "possible_keys": [
              "idx_product_id",
              "idx_product_reviews_status"
            ],
            "key": "idx_product_id",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "ref": [
              "const"
            ],
            "rows_examined_per_scan": 4,
            "rows_produced_per_join": 2,
            "filtered": "50.00",
            "cost_info": {
              "read_cost": "1.96",
              "eval_cost": "0.20",
              "prefix_cost": "2.36",
              "data_read_per_join": "3K"
            },
            "used_columns": [
              "product_review_id",
              "product_id",
              "user_id",
              "name",
              "advantages",
              "disadvantages",
              "comment",
              "rating_value",
              "ip_address",
              "is_buyer",
              "product_review_timestamp",
              "country_code",
              "city",
              "reply_user_id",
              "reply",
              "reply_timestamp",
              "helpfulness",
              "status",
              "storefront_id",
              "images_count",
              "vote_up",
              "vote_down"
            ],
            "attached_condition": "(`cscart_db`.`cscart_product_reviews`.`status` = 'A')"
          }
        },
        {
          "table": {
            "table_name": "cscart_users",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "user_id"
            ],
            "key_length": "3",
            "ref": [
              "cscart_db.cscart_product_reviews.reply_user_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 2,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "1.98",
              "eval_cost": "0.20",
              "prefix_cost": "4.54",
              "data_read_per_join": "14K"
            },
            "used_columns": [
              "user_id",
              "company_id"
            ]
          }
        },
        {
          "table": {
            "table_name": "cscart_companies",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "company_id"
            ],
            "key_length": "4",
            "ref": [
              "cscart_db.cscart_users.company_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 2,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.50",
              "eval_cost": "0.20",
              "prefix_cost": "5.24",
              "data_read_per_join": "13K"
            },
            "used_columns": [
              "company_id",
              "company"
            ]
          }
        },
        {
          "table": {
            "table_name": "cscart_country_descriptions",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "code",
              "lang_code"
            ],
            "key_length": "12",
            "ref": [
              "cscart_db.cscart_product_reviews.country_code",
              "const"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 2,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.50",
              "eval_cost": "0.20",
              "prefix_cost": "5.94",
              "data_read_per_join": "800"
            },
            "used_columns": [
              "code",
              "lang_code",
              "country"
            ]
          }
        }
      ]
    }
  }
}