Hello,
Thank you for contacting Rank Math and bringing your concern to our attention.
The Google Instant Indexing can post them automatically but just filtering by posts, categories, media, and products; not by specific categories and tags:
Please note that the instant indexing API should be used on live streaming and job posting websites.
For all other websites, it only guarantees to crawl – not indexing.
Please note that it is completely normal for a newly published post/page/website to take time before it gets crawled or indexed by Google. It depends on a lot of factors. Your posting frequency + the domain authority are just two of the many factors Google considers when indexing some new URL. Google assigns a crawl budget to your website depending on these factors (especially these two) and that has a direct effect on how soon or how late your content can get indexed.
You can check this link for more information:
https://rankmath.com/blog/google-indexing-api/
I hope that helps. Thank you, and please don’t hesitate to contact us if you need further assistance.