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Ethereum Smart Contracts and dApps Done Carefully

Solidity contracts, token systems and dApp frontends for Ethereum and EVM networks, written with tests, gas efficiency and external audits in mind.

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LoyaltyPoints.sol
Sample code

Ethereum development where mistakes are expensive

Ethereum is the most widely used smart contract platform, and its EVM standard also powers networks such as Polygon, Arbitrum, Optimism and Base. Smart contracts written in Solidity hold and move real value, and once deployed they are hard to change. That makes careful design, thorough testing and independent review far more important than in typical web development.

Ethereum and EVM chains are the right choice when you need the deepest liquidity, the widest wallet support and mature tooling, for tokens, DeFi protocols, NFTs, DAOs or on-chain verification. Layer 2 networks reduce fees for high-volume use. Solana suits apps that need very high throughput, while Hyperledger suits private enterprise networks where public tokens are unnecessary.

Nexzem writes Solidity with Foundry or Hardhat, using audited OpenZeppelin libraries, extensive unit and fuzz tests, and clear upgrade and admin controls. We prepare code and documentation for external security audits, which we strongly recommend before mainnet launch, and build the wallet-connected frontends and indexers that make contracts usable for real people.

Read Ethereum, the way we write it

A short, idiomatic sample. Scroll and the editor types each part while the note beside it explains why it is written that way.

LoyaltyPoints.sol
Sample code
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;
import {ERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";
// Audited OpenZeppelin building blocks, not hand-rolled token logic
contract LoyaltyPoints is ERC20, Ownable {
constructor() ERC20("Loyalty Points", "LPT") Ownable(msg.sender) {}
// Only the store can issue points; every mint is an on-chain event
function reward(address customer, uint256 amount) external onlyOwner {
_mint(customer, amount);
}
}

  1. line 7-10

    Audited OpenZeppelin building blocks, not hand-rolled token logic

  2. line 11-15

    Only the store can issue points; every mint is an on-chain event

What we build with Ethereum

Audit-ready Solidity smart contracts and dApps on Ethereum and EVM networks like Polygon and Base.

  1. 01

    Smart Contract Development

    Solidity contracts for payments, escrow, vesting, staking and business logic, built on OpenZeppelin standards with full test coverage and documentation.

  2. 02

    Token Development

    ERC-20, ERC-721 and ERC-1155 tokens with minting rules, supply caps, vesting schedules and role-based admin permissions documented for holders and auditors.

  3. 03

    dApp Frontends

    React and Next.js interfaces with wallet connection, transaction status, network switching and clear error messages for non-technical users.

  4. 04

    Layer 2 Deployment

    Deployment and configuration on Polygon, Arbitrum, Optimism or Base to cut transaction fees while staying compatible with Ethereum tooling.

  5. 05

    Contract Testing and Review

    Unit, fuzz and invariant tests plus internal review of existing contracts to catch logic bugs and common vulnerabilities before external audit.

  6. 06

    Indexing and Backend Services

    Event indexers, subgraphs and APIs that turn on-chain data into fast queries for dashboards, analytics and app features.

  7. 07

    Upgradeable Contract Design

    Proxy patterns, timelocks and multisig admin setups that allow controlled fixes while keeping users protected from sudden changes.

Why teams pick Nexzem for Ethereum

The checks every engagement has to pass before we call it done.

.github/PULL_REQUEST_TEMPLATE.md4/4 checked

  • - [x] Security-first approach

    Audited libraries, heavy testing and audit preparation reduce the risk of costly exploits.

  • - [x] Lower gas costs

    Efficient storage and logic design cut fees for your users.

  • - [x] Usable for real people

    Clear wallet flows and transaction feedback make dApps approachable for newcomers.

  • - [x] Honest chain advice

    We tell you when a public chain is unnecessary and a simpler database would do.

Ethereum mainnet vs Layer 2 networks

Ethereum mainnet offers the strongest security and decentralization in the ecosystem, but transaction fees can be high during busy periods. Layer 2 rollups such as Arbitrum, Optimism, Base and zkSync execute transactions off the main chain and post compressed data back to Ethereum, inheriting much of its security while offering far lower fees and faster confirmations.

Since the Dencun upgrade in 2024 introduced cheaper data storage for rollups, Layer 2 fees have dropped substantially, making them the default choice for consumer applications, games, loyalty programs and frequent payments. Mainnet remains appropriate for high-value assets, settlement and protocols where maximum security and composability with other mainnet protocols matter most.

Choosing a network also means considering liquidity, wallet and exchange support, bridging between chains and the maturity of each rollup's security model. Many projects deploy on one Layer 2 first and expand to others once demand is proven, keeping contracts portable across EVM-compatible networks.

How we build and test smart contracts

Contracts are written in Solidity using audited building blocks from OpenZeppelin wherever possible, rather than custom implementations of standard tokens or access control. Development uses Foundry or Hardhat, with unit tests for every function, fuzz tests that throw random inputs at contracts and invariant tests that check properties such as total supply never changing unexpectedly.

Static analysis tools such as Slither run in CI, deployments are scripted and repeatable, and every release is rehearsed on a testnet such as Sepolia. Administrative powers sit behind a multisig wallet such as Safe, often with a timelock so users can see upcoming changes before they take effect.

  • Audited libraries for tokens, access control and upgrades.
  • Unit, fuzz and invariant tests with high coverage.
  • Static analysis and gas reporting in CI.
  • Scripted deployments rehearsed on testnets.
  • Multisig and timelock control for admin functions.

Smart contract security essentials

Smart contracts are public, hold real value and are hard to change once deployed, so mistakes are expensive. Common vulnerability classes are well documented, and a disciplined process catches most of them before deployment. For contracts holding significant value, independent audits by specialist firms and a bug bounty program after launch are standard practice, not optional extras.

Security also extends beyond the contracts. Frontends can be compromised, admin keys can be phished and off-chain services such as indexers and oracles can fail. Monitoring on-chain activity for unusual transactions, protecting deployment keys with hardware wallets and having an incident response plan, including pause mechanisms where appropriate, limits the damage when something goes wrong.

  • Reentrancy, where external calls re-enter a function before state updates.
  • Missing or incorrect access control on privileged functions.
  • Price oracle manipulation through thin liquidity or flash loans.
  • Front-running and transaction ordering attacks.
  • Storage layout collisions in upgradeable contracts.
  • Signature replay across chains or contracts.
  • Unchecked return values from external token calls.

How Ethereum projects run

$ git log --graph --oneline main..delivery

  1. a429a50

    feat: use case and token design

    We define on-chain versus off-chain logic, roles, token rules and risks.

  2. 2fa02a3

    feat: contract architecture

    Contract structure, upgrade approach and admin controls documented upfront.

  3. 8304ee9

    feat: build and test

    Solidity development with unit, fuzz and integration tests on testnets.

  4. 31acc93

    feat: audit and launch

    External audit support, fixes and a controlled mainnet deployment.

  5. 5d409ee

    merge: monitor and maintain

    On-chain monitoring, frontend updates and governance support after launch.

What teams build with Ethereum

  • Loyalty points on a Layer 2

    A retail brand issues loyalty points as tokens on a low-fee Layer 2 network, with wallets created automatically for customers, so points can be earned, transferred and redeemed with partners without users needing crypto knowledge.

  • Tokenized real-world assets

    An asset manager represents fund units or property shares as permissioned tokens that only verified investors can hold, with transfer rules enforced on-chain and records reconciled with traditional registries off-chain.

  • NFT event ticketing

    Event tickets are issued as NFTs with rules for resale price caps and royalties, scanned at the venue for entry, and kept by attendees afterward as collectibles that grant perks at future events.

  • DAO treasury management

    A community organization holds its treasury in a multisig wallet, with proposals and votes recorded on-chain and approved payments executed transparently, giving every member visibility into how community funds are spent.

  • Stablecoin payments for freelancers

    A platform pays international freelancers in stablecoins on a Layer 2 network, settling in minutes with low fees, with compliance checks and off-ramp options to local bank accounts where regulations allow.

Where Ethereum sits in your stack

The tools we pair it with, layer by layer. Select a layer to see what it is responsible for.

Technologies often used with Ethereum

All 32 technologies

More in Cloud & Web3

Ethereum development FAQs

Something else on your mind? Ask a consultant and get a reply within one business day.

Should we build on Ethereum, Solana or Hyperledger?

Ethereum and EVM chains suit public apps that need wide wallet support and liquidity. Solana suits very high-throughput consumer apps. Hyperledger suits private consortium networks without public tokens. We help you decide whether you need a blockchain at all.

What drives smart contract development cost?

Contract complexity, number of contracts, token economics, upgradeability, frontend and indexer scope, and testing depth drive effort. External audit fees are separate. A fixed quote follows a free consultation.

Do you audit smart contracts?

We test and review contracts thoroughly and prepare them for audit, but we recommend an independent third-party audit before any mainnet launch that holds real value.

How do you reduce gas fees?

We optimise storage layout, batch operations, avoid unnecessary on-chain data, and recommend Layer 2 deployment when transaction volume is high.

Can contracts be changed after launch?

Only if designed for it. We can use proxy patterns with timelocks and multisig controls, or keep contracts immutable when trust requires it, and explain the trade-offs.

What is a Layer 2 network?

A Layer 2 network processes transactions outside Ethereum's main chain and posts proofs or compressed data back to it, inheriting much of Ethereum's security. Rollups such as Arbitrum, Optimism, Base and zkSync offer much lower fees and faster transactions, making blockchain applications practical for everyday use.

Why should contract administration use a multisig wallet?

A multisig wallet requires several independent keyholders to approve sensitive actions, such as upgrades or treasury withdrawals. It removes the risk of a single compromised key draining funds or changing contracts, and combined with a timelock, it gives users notice before changes take effect.

We work with clients across the USA, UK, Australia, UAE, New Zealand and India.

Where we work

Tell us what you're building.

A solutions consultant replies within one business day with a recommended stack, a rough estimate and a suggested team.

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