SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fa56b81e3cff3d23344bda4dbcc664a464b8040d55729bb57130783e7709af21' 
  AND token = 'MCvV1T1bBTqaS2ijxpPxzBzUGk7L8cNL6whamDvYZEg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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