SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39a9ebe13b7e6d90a26b84aaba3c12821fe4eaa50f0ea6fe739d3daef27816e5' 
  AND token = 'yznhVkDo5XFxRTllp24NX9NYWH46HfxJw7XIPIHMCeA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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