Getting Started with Blockchain Voting using Solidity

Why Blockchain Voting?

Traditional voting systems have a trust problem. How do you know your vote was counted correctly? Blockchain provides transparency and immutability — once a vote is recorded, it can't be changed or deleted.

Architecture

My UniVote system has three layers:

1. Smart Contract — Solidity contract on Ethereum Sepolia testnet
2. Backend — Node.js + Express API with MongoDB for user data
3. Frontend — React app with Web3.js integration

The Smart Contract

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract Voting {
    mapping(string => uint256) public voteCounts;
    mapping(address => bool) public hasVoted;
    
    event VoteCast(address voter, string candidate);
    
    function vote(string memory candidate) public {
        require(!hasVoted[msg.sender], "Already voted");
        voteCounts[candidate]++;
        hasVoted[msg.sender] = true;
        emit VoteCast(msg.sender, candidate);
    }
}

Key Learnings

• Gas fees — Even on testnet, transaction costs matter. I optimized the contract to minimize storage operations.
• Security — Smart contracts are immutable once deployed. Thorough testing is critical.
• UX — Web3 wallets are confusing for non-technical users. I added clear error messages and a step-by-step voting flow.

Demo

The app is deployed on Sepolia testnet. You can try it with a MetaMask wallet connected to the Sepolia network.

Source code: GitHub