Why Multi-Language? I run a niche content site about NBA jerseys. Basketball is global — fans in China, Japan, Korea, and Latin America search for the same jerseys in their own languages. By adding 4 additional locales, I 5x'd my addressable search traffic overnight. But manually translating 60+ articles into 4 languages? Not happening. Next.js 16 App Router next-intl v4 for routing and message handling MDX for content Claude API for translation Custom pipeline for batch processing content/ ├── en/ │ └── jerseys/ │ └── michael-jordan/ │ └── bulls-pinstripe.mdx ├── zh/ ├── ja/ ├── ko/ └── es/ Each locale gets its own content directory. The English version is the source of truth. export const locales = ['en', 'zh', 'ja', 'ko', 'es'] as const; export const routing = defineRouting({ locales, defaultLocale: 'en', localePrefix: 'as-needed', }); The as-needed prefix means English URLs stay clean while other locales get their prefix. I built a batch translator that reads English MDX, checks which translations are missing, sends to Claude API, and writes translated files preserving frontmatter. Every page needs alternates pointing to its translations. Both in page metadata AND in the sitemap. Missing translations gracefully fall back to English. No 404s. 63 English source articles → 267 total pages across 5 locales Zero manual translation work Build time: ~45 seconds for all 267 pages The site: JerseyToMe