SELECT 
  rating 
FROM 
  cscart_manual_rating 
WHERE 
  `object_id` = 2 
  AND `object_type` = 'company'

Query time 0.00013

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}