A full-stack Web3 NFT auction system built on Ethereum (Sepolia), featuring an upgradeable smart contract architecture and a production-style off-chain indexing backend.

This project demonstrates an end-to-end pipeline:

On-chain contract → Event indexing → Structured storage → Queryable API

The system consists of two major components:

• NFT Auction Market (UUPS Upgradeable)
• Supports ETH and ERC20 (USDC) bidding
• Chainlink Price Feeds for fair USD-based comparison

• Real-time blockchain event indexing
• Persistent storage in MySQL
• REST API for frontend consumption

• UUPS upgradeable architecture (ERC1967 standard)
• Dual-token bidding (ETH + USDC)
• Chainlink Oracle integration (ETH/USD, USDC/USD)
• Unified USD-based bid comparison
• Full auction lifecycle:
  • Create auction
  • Place bid
  • End auction
  • Settlement

• Event-driven indexer (based on go-ethereum)
• Automatic chain synchronization with cursor tracking
• Resumable indexing (fault-tolerant)
• REST API abstraction for frontend
• Clean separation of domain logic and infrastructure

• Implemented UUPS proxy pattern
• Ensured storage layout compatibility across versions
• Verified upgrade safety via V1 → V2 migration

• Integrated Chainlink Price Feeds
• Converted all bids into USD (18 decimals)
• Eliminated unfair advantages across token types

• Subscribed to contract events:
  • AuctionCreated
  • BidPlaced
  • AuctionEnded
  • AuctionCancelled
• Parsed logs into structured domain models
• Stored into relational database

• Maintained sync_cursors table
• Enabled restart-safe indexing
• Supports backfilling historical blocks

Frontend interacts with backend without touching blockchain:

• /api/auctions
• /api/auctions/:id
• /api/auctions/:id/bids
• /api/stats

nft-auction-protocol/ ├── onchain/ # Smart contracts (Hardhat) ├── backend/ # Indexer + API (Go)

contracts/ ├── MyNFT.sol ├── NFTAuctionMarketUUPS_V1.sol ├── NFTAuctionMarketUUPS_V2.sol

cmd/server # Entry point internal/indexer # Chain event processing internal/api # HTTP handlers internal/infra/db # DB models & repository layer internal/config # Configuration

• Solidity
• Hardhat
• OpenZeppelin (UUPSUpgradeable)
• Chainlink Oracle

• Go
• Gin
• GORM
• MySQL
• go-ethereum

• Docker Compose

Proxy (Auction): 0x085Ab5880dff3EDaE319948946E1df5bF683934e
V2 Implementation: 0x6E5F7Ba248F6deaC57ba0cfB565C0c7f24240f94
MyNFT: 0x7613Fea95c816346beaBE7132A29BC4Ab14BE83b

Covers:

• Auction creation
• ETH vs USDC bidding logic
• Price comparison via oracle
• Auction settlement
• Upgradeability validation

Run: npx hardhat test

Validated full workflow:

• Deploy NFT contract
• Mint NFT
• Approve marketplace
• Create auction
• Multi-round bidding
• Oracle price verification
• Auction settlement
• Contract upgrade (V1 → V2)

docker-compose up

or

go run cmd/server/main.go

GET /health
GET /api/stats
GET /api/auctions
GET /api/auctions/:id
GET /api/auctions/:id/bids

See /screenshots folder.

This project was built to explore the trade-offs between on-chain execution and off-chain indexing.

Key considerations include:

• Reducing RPC dependency via event-driven indexing
• Ensuring upgrade safety with UUPS proxy pattern
• Handling multi-token bidding with consistent price normalization

The goal was to simulate a production-like architecture while keeping the system minimal and testable.

• Production-style smart contract architecture
• Upgradeable protocol design
• Cross-token economic logic (USD normalization)
• Event-driven backend system
• End-to-end Web3 system integration

• WebSocket real-time updates
• Frontend integration (React / Next.js)
• Multi-chain support
• Advanced auction types (Dutch, sealed-bid)

M.X Du

Smart Contract Engineer (EVM)
Focused on protocol design, upgradeability, and backend indexing systems.