Johnny Lin/ notes
Sheet 02 — Selected work

Selected work

Production systems and focused prototypes — the problem, the decisions, the data flow and what each project proved.

STOREFRONTRetail + B2BADMINISTRATIONCatalog + settlementSTAFF WORKSPACETasks + resourcesCUSTOMER PORTALForms + personal recordsSHARED BUSINESS MODULESTransactions · records · documentsPOSTGRESQLRole grants · row-level securityPAYMENTS · OBJECT STORAGE · SCHEDULED OPERATIONS
Case study — Contract engineering
Cross-border Commerce & Operations Platform

First engineer responsible for architecture and delivery across four connected commerce and operations applications. Guide another engineer on internal applications and own platform integration, transaction controls and access boundaries.

TypeScript · Next.js · React · PostgreSQL · Drizzle ORM · Stripe · Vitest · Testcontainers · Turborepo · GitHub ActionsARCH — transactions · access boundaries · audit evidence · operations
CHECKOUTweb · mobilePAYMENT GATEWAYrouting · idempotencyone event shapeLOCAL PSPcardsLOCAL PSPbank transferLOCAL PSPwalletMULTIPLE LOCAL PROVIDERSLEDGERorders · settlementCHECKOUT → PSP → LEDGER
Case study — Software engineer
Cross-border e-commerce payments

Owned the payment gateway for a cross-border e-commerce platform: front-to-back integration and the data flow behind it, with local payment providers for different markets.

Java · Spring Boot · React · Oracle · Local PSPs · CODAARCH — payment routing · settlement flow
BROWSER WALLETNEXT.JS APPIDENTITY / TOKENTEST LENDINGconnect · signinterface + backendERC-3643 · OnchainIDproject contractsMongoDB · tx recordsserver actionswallet-signed actionsAPPLICATION INTEGRATION · TESTNET PoC
Hackathon — Web3 proof of concept
RWA Stock Lending — Hackathon

A testnet application connecting wallets, identity workflows and lending contracts through a Next.js interface and backend. Received an Honorable Prize at an RWA hackathon.

Next.js · React · TypeScript · MongoDB · Ethers.js · ERC-3643 · OnchainID · Lending contract integrationARCH — wallet · identity · transactions · lending
MANAGERON-CHAIN FUNDINVESTORcreate · configureEnzyme · fund shareswallet · holdingsCREATESUBSCRIBEREDEEMSepolia PoCSIGN → SUBMIT → CONFIRM → REFRESH
Internship project — Web3 application
On-chain Fund — Web3 proof of concept

A testnet fund-management interface connecting manager and investor journeys to Enzyme Protocol, from wallet connection to fund creation, subscriptions and redemptions.

Next.js · React · TypeScript · Ethers.js · Enzyme ProtocolARCH — wallet · fund creation · subscriptions · redemptions