JuntigerBuild notes and engineering retrospectives.https://juntiger.pages.dev/en/enMon, 29 Jun 2026 00:00:00 GMTNot Simply Trusting API Requests That Come From Outside the Apphttps://juntiger.pages.dev/en/engineering/hangangjari/20-app-attest-app-origin-trust/https://juntiger.pages.dev/en/engineering/hangangjari/20-app-attest-app-origin-trust/I used App Attest to check app-origin trust and treated state-changing requests with extra care.Tue, 23 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZRechecking an iOS App on Small iPhones After Looking Only at Large Screenshttps://juntiger.pages.dev/en/engineering/hangangjari/19-ios-visual-qa-small-iphones/https://juntiger.pages.dev/en/engineering/hangangjari/19-ios-visual-qa-small-iphones/A record of turning discomfort missed in iPhone 17 Pro Max-centered testing into device- and language-based visual QA.Tue, 23 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZHealthcheck Was Normal, but Notifications Were Not Safe Yethttps://juntiger.pages.dev/en/engineering/hangangjari-ops/healthcheck-push-recovery-gap/https://juntiger.pages.dev/en/engineering/hangangjari-ops/healthcheck-push-recovery-gap/After recovering from K3s DiskPressure, stale parking snapshots were compared like immediate previous values and pushed; I fixed it with a freshness guardFri, 19 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZThe Widget Was Not a Smaller Version of the Apphttps://juntiger.pages.dev/en/blog/hangangjari-series/08-widget-as-product-surface/https://juntiger.pages.dev/en/blog/hangangjari-series/08-widget-as-product-surface/How Hangangjari kept glanceable values and stale-state cues within iOS widget refresh constraints.Sun, 14 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZNumbers Alone Were Not Enough to Trust Public Datahttps://juntiger.pages.dev/en/blog/hangangjari-series/07-public-data-trust/https://juntiger.pages.dev/en/blog/hangangjari-series/07-public-data-trust/Why remaining spaces and congestion needed sources, updated times, and explicit unknown states beside them.Sun, 14 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZWhy I Focused on the Han River Instead of Expanding Nationwidehttps://juntiger.pages.dev/en/blog/hangangjari-series/06-why-focus-hangang/https://juntiger.pages.dev/en/blog/hangangjari-series/06-why-focus-hangang/I chose a scope I could verify directly and explain responsibly over a broader park app.Sun, 14 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZTurning a Home Server Into a Production Environmenthttps://juntiger.pages.dev/en/blog/hangangjari-series/05-infra-launch-and-retrospective/https://juntiger.pages.dev/en/blog/hangangjari-series/05-infra-launch-and-retrospective/A record of adding deployment, observability, and backup routines to a home server and reaching an App Store launch.Sun, 14 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZWhy the App Did Not Call Public Data Directlyhttps://juntiger.pages.dev/en/blog/hangangjari-series/04-backend-cache-and-workers/https://juntiger.pages.dev/en/blog/hangangjari-series/04-backend-cache-and-workers/How slow collection, prediction, and notification preparation moved into server workers so the screen could stay light.Sun, 14 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZAn iOS Experience That Had to Continue Before Opening the Apphttps://juntiger.pages.dev/en/blog/hangangjari-series/03-ios-client-and-widgets/https://juntiger.pages.dev/en/blog/hangangjari-series/03-ios-client-and-widgets/How widgets, notifications, deep links, and local cache kept the same park state connected.Sun, 14 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZWhy the Parking App Became a Hangang Visit Apphttps://juntiger.pages.dev/en/blog/hangangjari-series/02-product-scope-and-data-trust/https://juntiger.pages.dev/en/blog/hangangjari-series/02-product-scope-and-data-trust/The product decisions behind adding events, congestion, facilities, and notices while separating car and general screens.Sun, 14 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZThe Hangang Parking Widget I Built After Buying a Carhttps://juntiger.pages.dev/en/blog/hangangjari-series/01-origin-and-parking-widget/https://juntiger.pages.dev/en/blog/hangangjari-series/01-origin-and-parking-widget/How I reduced the parking checks I repeated before leaving into an app home screen and widget.Sun, 14 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZHangangjari System Overviewhttps://juntiger.pages.dev/en/engineering/hangangjari/00-system-overview/https://juntiger.pages.dev/en/engineering/hangangjari/00-system-overview/How collection, API, cache, and widgets share responsibility for the user's first screenSun, 14 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZRunning a Mini-PC Server Like a Real Servicehttps://juntiger.pages.dev/en/engineering/hangangjari/18-public-sre-retrospective/https://juntiger.pages.dev/en/engineering/hangangjari/18-public-sre-retrospective/A retrospective on separating user request paths, GitOps state, observability, and backupsSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZTelemetry That Does Not Send Location Coordinates to the Serverhttps://juntiger.pages.dev/en/engineering/hangangjari/17-privacy-minimal-telemetry/https://juntiger.pages.dev/en/engineering/hangangjari/17-privacy-minimal-telemetry/For a login-free app, I first decided what not to collect and kept only operational signalsSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZPublic-Data Translation Cache and Preserving Source Texthttps://juntiger.pages.dev/en/engineering/hangangjari/16-localization-source-and-translation-cache/https://juntiger.pages.dev/en/engineering/hangangjari/16-localization-source-and-translation-cache/I separated UI strings, curated translations, machine translations, and Korean fallbackSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZPush Outbox and Suppression Audithttps://juntiger.pages.dev/en/engineering/hangangjari/15-push-suppression-outbox-delivery-audit/https://juntiger.pages.dev/en/engineering/hangangjari/15-push-suppression-outbox-delivery-audit/I recorded sent notifications and stopped notifications with their reasons in the same systemSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZWhy Parking Forecasts Need Confidencehttps://juntiger.pages.dev/en/engineering/hangangjari/14-parking-forecast-baseline-confidence-backtest/https://juntiger.pages.dev/en/engineering/hangangjari/14-parking-forecast-baseline-confidence-backtest/I used p10, p50, p90, risk, and backtests so forecasts do not look like one correct answerSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZKeeping Stale Responses from Looking Fresh: Redis Cachehttps://juntiger.pages.dev/en/engineering/hangangjari/13-redis-hot-stale-cache-fallback/https://juntiger.pages.dev/en/engineering/hangangjari/13-redis-hot-stale-cache-fallback/I separated fast responses from last-success values so cache does not mislead usersSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000Zsource catalog and ingestion runhttps://juntiger.pages.dev/en/engineering/hangangjari/12-source-catalog-and-ingestion-runs/https://juntiger.pages.dev/en/engineering/hangangjari/12-source-catalog-and-ingestion-runs/I separated collection plans from execution results to explain freshness and failures by sourceSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZBundling First-Screen Values into One Response: home-summaryhttps://juntiger.pages.dev/en/engineering/hangangjari/11-home-summary-api-contract/https://juntiger.pages.dev/en/engineering/hangangjari/11-home-summary-api-contract/I put parking, outing, forecast, and source status into one response so the app and widgets start from the same valuesSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZSnapshot Storage for WidgetKithttps://juntiger.pages.dev/en/engineering/hangangjari/10-widget-snapshot-architecture/https://juntiger.pages.dev/en/engineering/hangangjari/10-widget-snapshot-architecture/I let widgets outside the app safely read the last display value and refresh stateSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZThe Order I Check When Data Looks Stalehttps://juntiger.pages.dev/en/engineering/hangangjari/09-infrastructure-and-observability/https://juntiger.pages.dev/en/engineering/hangangjari/09-infrastructure-and-observability/I narrowed stale-data causes by checking the edge, API, workers, cache, and DB in orderSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZLeaving Deployment as Records, Not Memoryhttps://juntiger.pages.dev/en/engineering/hangangjari/08-ci-cd-and-release/https://juntiger.pages.dev/en/engineering/hangangjari/08-ci-cd-and-release/Tests, images, desired state, and migration order became one repeatable release pathSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZWhat I Filtered Before Sending Push Notificationshttps://juntiger.pages.dev/en/engineering/hangangjari/07-push-notification-architecture/https://juntiger.pages.dev/en/engineering/hangangjari/07-push-notification-architecture/Subscription settings, quiet hours, freshness, and audit records choose what not to send firstSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZHow Not to Present Forecasts as Current Valueshttps://juntiger.pages.dev/en/engineering/hangangjari/06-forecast-and-data-science/https://juntiger.pages.dev/en/engineering/hangangjari/06-forecast-and-data-science/Forecast workers, confidence, and backtests expose uncertainty before arrivalSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZA Parser That Separates No Data From Collection Failurehttps://juntiger.pages.dev/en/engineering/hangangjari/05-data-parsing-and-source-policy/https://juntiger.pages.dev/en/engineering/hangangjari/05-data-parsing-and-source-policy/Official source grades, schema drift, and ingestion runs explain why a screen is emptySat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZWorkers and CronJobs Running Outside the APIhttps://juntiger.pages.dev/en/engineering/hangangjari/04-workers-and-jobs/https://juntiger.pages.dev/en/engineering/hangangjari/04-workers-and-jobs/Collection, forecasts, push, and reference-data sync run separately from user requestsSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZHow I Split Responsibilities Between Postgres and Redishttps://juntiger.pages.dev/en/engineering/hangangjari/03-cache-and-db-architecture/https://juntiger.pages.dev/en/engineering/hangangjari/03-cache-and-db-architecture/Records and audit trails stay durable, while rebuildable responses live in cacheSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZDesigning Thin FastAPI Routeshttps://juntiger.pages.dev/en/engineering/hangangjari/02-backend-api-architecture/https://juntiger.pages.dev/en/engineering/hangangjari/02-backend-api-architecture/HTTP routes handle requests and responses while screen composition moves into application use casesSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000ZHow the SwiftUI App and WidgetKit Read the Same Statehttps://juntiger.pages.dev/en/engineering/hangangjari/01-ios-client-architecture/https://juntiger.pages.dev/en/engineering/hangangjari/01-ios-client-architecture/A structure where SwiftData and App Group snapshots keep values consistent outside the appSat, 13 Jun 2026 00:00:00 GMT2026-06-29T00:00:00.000Z