Laravel SEO sitemap indexing issue

I'm developing a robust dynamic XML sitemap solution for Laravel applications, specifically targeting high-traffic, content-heavy platforms. My goal is to ensure auto-updating and future-proof indexing for millions of URLs.

The core technical hurdle I'm facing revolves around optimizing the sitemap generation process to minimize server load while maximizing indexing efficiency for search engines. For sites with rapidly changing content or a sheer volume of new pages, a full sitemap regeneration on every significant update is proving resource-intensive and can impact crawl budget.

I'm looking for advanced strategies or architectural patterns to handle granular updates within a massive dynamic sitemap. Specifically, how do you manage efficient delta updates for XML sitemaps when only a fraction of URLs change, and how can these changes be signaled to search engines (e.g., using lastmod, changefreq, or dedicated sitemap index files) without forcing a full re-crawl of unchanged sections? Are there battle-tested approaches for maintaining sitemap integrity and performance at enterprise scale?