Indexation at two million URLs: a field guide

"Not indexed" is not one problem. At seven figures of URLs it is at least three, and the fix depends entirely on which stage is failing.

Discovery, rendering, selection

• Discovery: the URL is not linked or sitemapped where crawl actually flows.
• Rendering: the content depends on client-side execution that does not resolve cheaply.
• Selection: Google sees it and decides it is a duplicate or not worth keeping.

Treating a selection problem as a discovery problem (more sitemaps, more links) just pours crawl into pages that will be dropped anyway.