Solidity & Cairo Smart Contracts

I will develop tested smart contracts in Solidity or Cairo for EVM and Starknet

Jedidiah GabrielProduct engineer · Kaduna, Nigeria · Replies within 24 hours

Solidity & Cairo Smart Contracts flyer: Contracts that do what they say.

About this gig

A smart contract can't be patched quietly after launch, so the testing has to happen before it.

I write smart contracts in Solidity for EVM chains and Cairo for Starknet, standard or fully custom. You describe the goal; I find the edge cases. Every contract starts from a spec, uses audited OpenZeppelin parts where they fit, and ships with tests for every path. I deploy to testnet first, verify the contracts, and build the dApp screens people use to reach them.

What you get:

A written spec of what the contract allows and forbids
A threat model: stalls, frozen oracles, griefing, key loss
Contracts in Solidity or Cairo: tokens, NFTs, vesting, staking, escrow, registries
Unit and integration tests with Foundry, Hardhat or Starknet Foundry
Deployment scripts and verified testnet contracts
Optional dApp frontend in Next.js with wallet connection
An internal security review and audit preparation

My Cairo work includes Bilateral Escrow (open source), LandReg3, a land registry live on Starknet Sepolia, and contributions to MusicStrk and other Starknet projects.

Send me what the contract should do, who can call what, and which chain your users are on.

Use cases

Tokens

ERC-20 or Starknet tokens with vesting, caps and roles.

NFTs and memberships

Collections, membership passes and on-chain metadata.

Staking and rewards

Stake, earn and unstake with safe reward accounting.

Vesting and payroll

Token or USDC streams for teams and investors.

Escrow and settlement

Funds released only when conditions are met.

Registries

Land, assets, certificates or credentials recorded on-chain.

Custom logic

Rules no template covers, designed from a spec and a threat model.

Account abstraction

Starknet accounts, session keys and paymasters for gasless apps.

What changes

Today

You have a token or protocol idea and nobody to write and test the contract
Copied contracts carry bugs nobody on your team can spot
The contract works, but users can't find their way around the frontend
You want Starknet's low fees, and Cairo developers are scarce

After

Contracts written from a clear spec, with tests for every path
OpenZeppelin components and known patterns instead of clever code
Deployment scripts and verified contracts on testnet, then mainnet
A dApp frontend with wallet connection on Viem, Wagmi or starknet.js

How it works

01Write the spec
02Implement the contract
03Test every path
04Deploy to testnet
05Verify and ship the dApp

Compare packages

Package	Starter$280	Business$850	Scale$2,400
What it is	One contract (token, NFT, vesting or similar) with tests and testnet deployment	Up to 3 interacting contracts, full test suite, deployment scripts and docs	Protocol build with dApp, upgrade path, internal security review and mainnet
Contracts	1	Up to 3	Up to 8
Language	Solidity or Cairo	Solidity or Cairo	Both if needed
Unit and integration tests	✓	✓	✓
Testnet deployment	✓	✓	✓
Deployment scripts	–	✓	✓
Technical documentation	–	✓	✓
dApp frontend with wallet connection	–	–	✓
Upgradeability and admin controls	–	–	✓
Internal security review report	–	–	✓
Mainnet deployment support	–	–	✓
Delivery	5 days	12 days	24 days
Revisions	2	3	4

Add-ons

Faster delivery+30% of the package
Internal security review with written findings+$250
Testnet deployment and verified contract+$90
Written documentation for your team+$50
90 days of support and small changes+$240

Built before

Bilateral EscrowOpen-source Cairo contract that holds a buyer's payment and a merchant's return bond until delivery terms are met.github.com LandReg3Land registry on Starknet Sepolia: each parcel is an ERC721 token and its documents open only to the wallet holding it.sepolia.voyager.online MusicStrkOpen-source, self-custodial record label factory on Starknet that I contribute to.github.com Starknet open sourceContributions across Starknet gaming and DeFi projects through OnlyDust.app.onlydust.com

Who it's for

Web3 startups
Fintechs
DAOs and communities
Game studios
Enterprises piloting blockchain

What I'll need from you

What the contract should do, and what it must never allow
Who can call which functions (owner, users, admins)
Target chain and any tokens involved
Existing code or contracts, if any

Questions, answered

Do you do audits?

I do internal security reviews and prepare contracts for audit with tests, documentation and a list of known issues. For contracts that will hold significant funds, I recommend an independent audit firm as well and work with them on fixes.

Solidity or Cairo?

Solidity if your users and liquidity are on Ethereum, Base or another EVM chain. Cairo on Starknet if you want low fees, account abstraction built in, or zero-knowledge features.

Can you build the frontend too?

Yes. Next.js with Viem and Wagmi for EVM chains, and starknet.js with starknet-react for Starknet.

Who owns the code and accounts when we finish?

You do. Code goes to your repository, and services run on accounts in your name, so you are never locked to me. I hand over logins, keys and a short guide.

How do I pay, and can we work outside Fiverr?

Order on Fiverr if you prefer its protection. For direct work I invoice in USD and accept bank transfer, card through Paystack or Stripe, and USDC.

What if my project doesn't fit a package?

Send a message describing what you need. I reply with a custom offer priced to the actual scope, often after a short call.

The thinking behind it

Trust Should Start With the First OrderBuyers won't pay first and sellers won't ship first. Jedidiah Gabriel on escrow smart contracts with return bonds, timeouts and a dispute path, so two strangers can trade without a middleman holding the money.A Land Title Nobody Can Quietly ChangeLand records get altered, duplicated and lost, and buyers can't check history before they pay. How a tokenized land registry records ownership permanently while keeping title documents private to the owner.