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web3Monad Testnet

RoastWager

A prediction market where the smart contract is the source of truth

RoastWager is a full-stack opinion-and-prediction market dApp on Monad. Users post an opinion, stake tokens on a side, and claim rewards once the market resolves — with the contract holding the truth and an event-driven backend keeping the UI fast and consistent.

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RoastWager

The problem

A trustless prediction market has to keep the money and the outcome on-chain, but reading a chain directly from the browser is slow and inconsistent for a social feed. The challenge was to make create → vote → resolve → claim fully on-chain while still delivering an instant, feed-like experience.

What I built

I split the system into three roles: the smart contract is the source of truth, the backend is the synchronization engine, and the frontend owns the user experience. An event-driven listener tails the contract's events on Monad and mirrors them into a database, so the UI reads a consistent API instead of querying the chain on every render.

Architecture

Smart contract

Solidity + Foundry

Source of truth. Exposes createWager, vote, resolve, and claim, and emits WagerCreated / Voted / Resolved / Claimed events. Refunds automatically when one side has no bettors or both pools are equal.

Backend listener

Node.js + Hono + viem + Supabase

Synchronization engine. Reads Monad chain events, syncs them into Supabase, and serves a REST API to the frontend. Rate-limited per IP with an auto-reconnecting event listener.

Frontend

Next.js + wagmi + RainbowKit

User experience. Queries the backend API (not the chain) for UI consistency, with optimistic updates so pending posts appear immediately.

Engineering highlights

  • IDs are scoped by contract address, so markets stay valid across contract migrations.
  • Automatic refunds when a side has no bettors, or when both pools hold equal value.
  • Optimistic UI — pending posts show up instantly, before the transaction confirms.
  • XP / level system: +10 XP per vote, then +25 XP for winners and +5 XP for losers on resolution.
  • Blind markets hide pool details while a market is still active.

Stack

Smart contractSolidity, Foundry
BackendNode.js, Hono, Supabase, viem
FrontendNext.js, wagmi, RainbowKit
Storage & infraSupabase (PostgreSQL), Railway, Vercel, Pinata (optional images)

Deployed contract (Monad Testnet): 0x09AcB861808f014673dAED424c1ACa4a9462559E