SELECT 
  `rating` 
FROM 
  `cscart_absolute_rating` 
WHERE 
  `object_type` = 'company' 
  AND `object_id` = 630

Query time 0.00061

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}