SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6e47643da0a35c50fb95bf9d0d04f8bb62324f778bcc1bbf042aa58a6ef8349' 
  AND token = 'FJ/+n7FwRW+9vkaOBnQRgKagfiVbFvQe3ZdprRc6czY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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