# Engineering Guides | Mettevo

Migration and architecture guides from the Mettevo engineering team, written from production work rather than release notes.

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## [Next.js 16.3 Upgrade: What Actually Changes and What It Costs](https://mettevo.com/guides/nextjs-16-3-upgrade-guide)

Next.js 16.3 splits into a free performance upgrade and an opt-in migration. What each half costs, measured on a production headless build.

**Author:** Oleksii Turovskyi · **Updated:** 2026-08-16 · **Reading time:** 12 min