SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc3bd0ae978da3d4f849a5818488371d6890d2a147925d54b21d546daf3bdecc' 
  AND token = 'Kfe8WgX9coUjxNp4Iqk/ROjQ3CQwIJVvO/X5n5kTo+Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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