SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f70e003573634af0990616043fb9ffe52a108dcdacf739e0154cd69201b849a8' 
  AND token = 'pIBLLyRWg7IXRALJHmwHQMl4I0A75duXPDuKJdFSyC0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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