SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '1f171f87794ced63912f652e8a156538cae1cdf02340288101b7d558dd92819b' 
  AND token = '15neY/KjIlg/Z79l+YHRl+c+ubVzywdtH/A556WOBLw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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