SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3bb16756f83c92e112a767800481f25298e8c6b24bd263d2313f63ac66d75235' 
  AND token = 'GpYG/A2Mj+gkWaijBnwF3WhpP7feZNXshFGY1+Kxelk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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