SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '784007f6a3a4a49b854ca4ecc4e04263137b3577e624d1780d9886fcb6338f36' 
  AND token = '1zNSibOg4wrL0aM0/oeEF72GGVnJPZvvHF+BMwtRtXU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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