One or more indexers are invalid. Make sure your Magento cron job is running. I met with such issue. I know I can can update indexers from the command line but again, I'd have to do it every time you made a change that invalidated them. How to create the cron job and make it automatically updated by the Magento 2 CLI? so that no need to make it changed every time. I am not familiar with the code, please kindly tell me the detail step by step.