SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '912a3012087178e4760b2fce0062d7de17da949df5bc3581dc181313a854b76b' 
  AND token = 'UpTaR9Z+/Q+u/2huTkbztI6hJ+RHzlwlG87imM9jjP4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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