SELECT 
  rating_value, 
  COUNT(1) count 
FROM 
  cscart_company_product_review 
WHERE 
  `company_id` = 366 
  AND `status` = 'A' 
GROUP BY 
  rating_value

Query time 0.45777

JSON explain

{
  "query_block": {
    "select_id": 1,
    "filesort": {
      "sort_key": "PR.rating_value",
      "temporary_table": {
        "nested_loop": [
          {
            "table": {
              "table_name": "PR",
              "access_type": "ALL",
              "possible_keys": ["idx_product_id"],
              "rows": 25675,
              "filtered": 100,
              "attached_condition": "PR.`status` = 'A'"
            }
          },
          {
            "table": {
              "table_name": "P",
              "access_type": "eq_ref",
              "possible_keys": ["PRIMARY"],
              "key": "PRIMARY",
              "key_length": "3",
              "used_key_parts": ["product_id"],
              "ref": ["dev_db.PR.product_id"],
              "rows": 1,
              "filtered": 100,
              "attached_condition": "P.company_id = 366"
            }
          }
        ]
      }
    }
  }
}