Devy

Devy Archive

Notes on backend engineering, platform operations, and the decisions behind them.

33 posts · 8 series · 75 tags

Recent Posts

2026-07-060

Operating a CS Support System with Spring AI - From Function Calling to an Operator Suggestion Workflow

How a Spring AI customer-support draft system moved from function calling to parallel lookups, QA, error diagnosis, and an operator-review workflow in production.

spring-aispring-bootaillmcs

2026-07-040

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.

i18ncloud-runpdfweasyprint

2026-06-260

Service Internationalization (4) - The Backend's Part: User Language, Timezone, and Document Locale

Translate the front end alone and the server keeps mixing Korean back in through its responses and documents. This is the story of how the backend stored each user's language and timezone, carried them along in the authentication context, and pushed the locale all the way through to responses and documents.

i18nspring-bootjavabackend

2026-06-170

Service Internationalization (3) - Zero-Downtime Rollout with a GrowthBook Kill Switch

Even with all translations ready, flipping the switch for everyone at once is risky. The story of funneling locale decisions into a single choke point and rolling out i18n with zero downtime, gradually, via a GrowthBook kill switch.

i18nnextjsgrowthbookfeature-flag

2026-06-030

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.

i18nnextjsgcstypescript