Posts
All the articles I've posted.
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Data Engineering Study #1 — Coffee and coffee Are Different Values
I started studying data engineering. Two days of notes on deliberately creating a dirty CSV to see how case sensitivity and empty values break aggregations, plus the principle of never touching raw data and cleaning it in staging instead, and learning UPPER, CASE, and COALESCE.
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Real-Device Testing on App-in-Toss — Stuck on Direct Phone Connection, Solved with ait deploy
Starting the August vibe coding challenge, I tried real-device testing on App-in-Toss with my Galaxy Flip4 and only got 'A problem occurred while running the app.' I checked wifi, logs, and even TCP settings but couldn't fix it — turns out the whole approach was wrong. The answer was to build a bundle with `npx ait deploy` and send a test push.
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Feature-by-Feature Study #2 — JWT Authentication: An Access Pass the Server Doesn't Remember
How JWT solves the weakness of the session approach (the server having to remember every session). Covers the structure that packs information into the token itself (header, payload, signature), the trap that the payload is just base64, not encryption, code for creating and verifying tokens with jjwt, and the new problem JWT introduces (no revocation).
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Studying by Feature #1 — Session-Based Authentication: Why Doesn't HTTP Remember Me?
I decided to dig into features like login/auth, reservations, and payments one by one. The first topic is session-based authentication. Covers authN vs authZ, the fundamental problem caused by HTTP being stateless, how sessions work like a 'locker number tag,' Spring Security, why passwords are hashed with BCrypt, and the weaknesses of the session approach.