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Service Localization for Japan Expansion

Day1 Company · Jun 2026 - Aug 2026

Spring BootSpring OAuth2ReactTypeScriptGrowthBookGCSCloud Run

Tasks

  • •Added LINE, Google, and Apple social login and LINE friend-add integration to offer Japanese users more ways to access the service
  • •Built an app internationalization (i18n) foundation that separates localized text from app code, loading language packs from GCS at runtime so translations can change without redeploying the app
    • •Fall back to bundled text if language-pack loading fails, and control rollout scope with a GrowthBook kill switch
  • •Implemented user language and timezone settings APIs and screens, propagated language codes through authentication data, and added language-based home banner targeting
  • •Reworked completion certificates and level-test reports into HTML templates and language-specific strings, replacing per-language background image redesigns with multilingual document generation
    • •Separated responsibilities: the backend sends issuance events and a Cloud Run service renders HTML and localized text into PDFs

Achievements

  • •Completed backend and app localization required for entering the Japanese market
  • •Enabled translation updates without app redeployment and document localization without recreating images for each language

Related Posts

Service Internationalization (1) - Stripping Out Hardcoded Korean

Frontend internationalization, kicked off ahead of our launch in Japan. Here's how we settled on a locale model, managed our messages, and flowed the locale through the entire system.

2026-05-19

Service Internationalization (2) - Serving Language Packs: Bundle, GCS Runtime Load, and Cache

If you ship translations together with the app, every one-line copy fix means a redeploy. This post covers the structure that loads language packs from GCS at runtime and falls back to the bundle, plus the cache problem where copy wouldn't change even after deploying.

2026-06-03

Service Internationalization (5) - From Image-Baked Documents to HTML: Multilingual PDF Rendering

For a long time, the language of our certificates and reports was baked into images. This is the story of moving image-based documents to HTML templates plus Cloud Run rendering, so that adding a new language became a single JSON file.

2026-07-04