SELECT 
  product_review_id 
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 (81606) 
  AND cscart_product_reviews.status = 'A' 
GROUP BY 
  cscart_product_reviews.product_review_id

Query time 0.00061

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "1.56"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_product_reviews",
            "access_type": "ref",
            "possible_keys": [
              "PRIMARY",
              "idx_product_id"
            ],
            "key": "idx_product_id",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "ref": [
              "const"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 0,
            "filtered": "10.00",
            "index_condition": "(`webmarco`.`cscart_product_reviews`.`product_id` <=> 81606)",
            "cost_info": {
              "read_cost": "1.00",
              "eval_cost": "0.02",
              "prefix_cost": "1.20",
              "data_read_per_join": "167"
            },
            "used_columns": [
              "product_review_id",
              "product_id",
              "country_code",
              "reply_user_id",
              "status"
            ],
            "attached_condition": "(`webmarco`.`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": [
              "webmarco.cscart_product_reviews.reply_user_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 0,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.10",
              "eval_cost": "0.02",
              "prefix_cost": "1.32",
              "data_read_per_join": "659"
            },
            "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": [
              "webmarco.cscart_users.company_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 0,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "0.10",
              "eval_cost": "0.02",
              "prefix_cost": "1.44",
              "data_read_per_join": "975"
            },
            "used_columns": [
              "company_id"
            ]
          }
        },
        {
          "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": [
              "webmarco.cscart_product_reviews.country_code",
              "const"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 0,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "0.10",
              "eval_cost": "0.02",
              "prefix_cost": "1.56",
              "data_read_per_join": "40"
            },
            "used_columns": [
              "code",
              "lang_code"
            ]
          }
        }
      ]
    }
  }
}