HACKATHON

Three Days, Five People, One Plan: My GWDC Hackathon Story

Fintech project built in three days.

Ria Choi • October 8th, 2026

About the GWDC Hackathon

GWDC stands for Global Web3 Developer Conference. It is a global developer event that links developers, tech companies, and investors, with a focus on Web3 and AI.

This was the second edition. The first one took place in Hong Kong in February, and this one moved to Seoul. The event ran from September 28 to 30 at the aT Center in Seoul, and organizers expected 8,000+ attendees, 500+ core developers, and 100+ investment firms.

This Year's Topic

The big theme was AI × Web3. The slogan was "For Builders, By Builders," and the hackathon covered up to five public blockchain ecosystems.

The submission rules were strict. Each team needed a public GitHub repo, a demo video under three minutes, and a pitch deck. Finalists had to present on the Innovation Stage, and teams could have up to five members.

Sponsors and Partners

The conference was hosted by Web3Labs and cohosted by Techub News, Hypai Labs, and TokenPost.

or the hackathon itself, two big names stood out. TRON joined as an ecosystem partner, and Microsoft provided cloud infrastructure for development, testing, and deployment. Eligible projects could also get free Microsoft cloud credits for up to six months.

Our Team

We were a team of five. Each person owned one clear area.

How We Managed Everything in 3 Days

┌──────────────┐  wallet login(JWT)   ┌───────────────────────────────────────────────┐
│ Owner Wallet │ ───────────────────► │ Next.js Frontend                              │
│ (사용자 키)    │ ◄── typed-data 서명, │  요청·검토·승인·진행·결과                        │
└──────┬───────┘     deploy/fund     └───────────────┬───────────────────────────────┘
       │ deploy FlowwTaskAccount                     │ HTTP (owner-JWT) + SSE
       │ approve allowance / fund()                  ▼
       │                     ┌──────────────────────────────────────────────────────┐
       │                     │ Spring Boot Backend (Java 21, 모듈형 단일 서버)          │
       │                     │  ├ Auth/Security (지갑 로그인 → JWT, 소유권 검사)       │
       │                     │  ├ Task / Mandate (버전·상태 머신)                      │
       │                     │  ├ Merchant Registry (merchantId → 신뢰 수취인)         │
       │                     │  ├ Quote 수집 (시뮬레이션 약국 A/B/C)                   │
       │                     │  ├ AI 모듈 ──────────► Kiln qwen3-32b (후보 선택만)     │
       │                     │  ├ Policy Engine (ALLOW/DENY, reasonCode)              │
       │                     │  ├ TaskAccount 모듈 (prepare/bind/approval/…/reconcile)│
       │                     │  ├ Payment (payment intent, paymentId, reconcile)      │
       │                     │  ├ Fulfillment 검증                                    │
       │                     │  └ Events / Evidence (조회·내보내기)                    │
       │                     └───────┬───────────────────────────┬──────────────────┘
       │                             │ JPA / Flyway V1–V5        │ RPC (조회·송신)
       │                             ▼                           ▼
       │                     ┌───────────────┐       ┌────────────────────────────────┐
       └───────────────────► │ PostgreSQL 16 │       │ Sepolia (11155111)             │
                             └───────────────┘       │  FlowwTaskAccount (구매 1건당 1개)│
                                                     │  fUSDC fixture (ERC-20, 6 dec) │
              server-managed wallets (서버 시크릿) ──►  │  executor: approveMandate 릴레이,│
              executor ≠ fulfillmentReporter ≠ owner │            executePayment      │
                                                     │  reporter: confirmFulfillment  │
                                                     └────────────────────────────────┘

We used Confluence to keep our plans, specs, and decisions in one place. Nothing got lost in chat messages.

We also had an architect on the team. This made a big difference. He shaped the overall structure early, so the rest of us could focus on our own parts. The journey was smooth because the foundation was clear.

Vibe Coding, But With a Plan

Three days is not much time. So we made a bold choice.

Day 1 and Day 2: Planning only. We mapped out features, APIs, data flow, and security rules.

Day 3: We fed our detailed prompts to AI and let it write the code.

The goal was simple. Have a solid plan before writing a single line.

I was in charge of the backend server. AI can write code fast, but it does not always follow the rules. So I checked every output carefully.

Conclusion

It was an awesome opportunity. But honestly, I expected something more real.

Most participants were vibe coders. Many results looked very similar. With pitch decks, demo videos, and VC judges, it felt more like a business competition than a true coding challenge.

Still, I learned a lot. The biggest lesson was this: plan first, build second. This matters even more in fintech, where the security flow is a core part of the project. AI can speed up coding, but it cannot replace a clear plan and careful review.

I would join again, now with sharper expectations and an even better plan.