Another approach to this is just building a static site (Gatsby or w.e)…if the content is not something that needs to be immediately published - you could do something quite simple via an API that writes a JSON file to a storage bucket - and on a regular basis like every evening it kicks off a build, deploying and SEOing the newly added content… of course this also has scaling issues if you are building 100k + pages(unless done incrementally) - but if you want really good SEO - you cant beat serving static content. This is also not a bad idea until you DO reach scaling issues, and then you re-engineer when you actually have users actively publishing content all the time…
