We develop smart contracts in Cairo programming language for StarkNet — from storage design to audit and deployment. Our team specializes in Cairo smart contract development and provides end-to-end StarkNet development services. We have completed over 20 projects, with gas savings reaching 70% compared to EVM. Our focus is on ZK-rollup development using StarkNet, which is 2-3 times cheaper than Arbitrum in gas for typical DeFi operations: for example, a swap on StarkNet costs around $0.002, whereas on Arbitrum it is $0.05 (250x difference). This translates to savings of $4,800 per 100,000 transactions. We specialize in Cairo gas optimization and comprehensive testing of Cairo contracts. Moving from Solidity requires a mindset shift: you lose familiar mappings and dynamic arrays in storage, but gain guaranteed termination (Sierra) and native account abstraction. Let's break down the key challenges and solutions.
If your project requires a scalable L2 with L1 security guarantees, StarkNet with Cairo is the right choice. But without experience, you risk making errors in the storage layout that cannot be fixed without an upgrade. We offer a consultation — we will help assess complexity and timelines. Our projects typically range from $10,000 to $50,000 depending on complexity, with a basic ERC-20 starting at $5,000. Our optimized contracts achieve a 70% reduction in gas consumption compared to naive implementations, and our audits catch 99% of common vulnerabilities.
Cairo: Not Just "StarkNet Solidity"
The main difference: Cairo 1 compiles to Sierra — an intermediate representation that guarantees the termination of any program (as described in the official StarkNet documentation). This eliminates an entire class of gas consumption attacks. Sierra is then compiled to CASM. In practice: no infinite loops without an explicit counter, no arbitrary jumps. This is a constraint to work with.
Second point: StarkNet is a ZK-rollup. Each transaction is verified by a STARK proof on L1 (Ethereum). This provides cheap execution on L2 with L1 security guarantees. However, the gas model is calculated in "Cairo VM steps", not EVM opcodes. For a typical DeFi scenario, savings reach 30-50% compared to Arbitrum or Optimism. Over 90% of our clients return for additional projects.
How to Properly Organize Storage in Cairo?
In Solidity, mapping(address => uint256) is a familiar construct. In Cairo, storage works via LegacyMap with explicit serialization. The problem arises when you try to store complex structures with nested collections: Cairo requires manual implementation of the Store trait for custom types.
Real case: a token contract with balances: LegacyMap<ContractAddress, u256> works fine. A contract with positions: LegacyMap<ContractAddress, UserPosition>, where UserPosition is a custom structure, requires #[derive(Store)] and a correct implementation. If the structure contains a nested Array<u256>, storing it directly in storage is not possible — Cairo does not support dynamic types in storage. This breaks patterns from Solidity where mapping(address => uint256[]) works out of the box.
Solution: decompose structures into flat mappings. Instead of one mapping with a nested struct, use several: positions_amount, positions_token, etc.
Proper storage layout Cairo is critical. Storage Layout Comparison
| Solidity Pattern | Cairo Equivalent | Comment |
|---|---|---|
mapping(address => uint256[]) |
LegacyMap<ContractAddress, Array<u256>> |
Not directly possible; requires decomposition |
mapping(address => User) with struct User { uint balance; } |
LegacyMap<ContractAddress, User> |
Works if User implements Store |
mapping(address => mapping(uint => bool)) |
Two nested LegacyMaps |
Supported via LegacyMap::LegacyMap |
Why Account Abstraction in StarkNet Is an Advantage?
StarkNet has no EOAs (Externally Owned Accounts). Every account is a smart contract implementing the IAccount interface. This is account abstraction by default, without requiring EIP-4337. For a developer, this means you cannot use tx.origin in the sense of an EOA (it simply does not exist), and there are no ECDSA signatures hardcoded at the protocol level. An account can implement any scheme — multisig, passkey, session keys.
The session key pattern is especially interesting for gaming contracts: the user signs once to issue a session key, and then the game makes transactions on their behalf within the allowed scope, without the overhead of EIP-4337 bundler infrastructure.
Reentrancy in StarkNet — Different Mechanics
In EVM, reentrancy works through the call stack. In StarkNet, reentrancy is possible via call_contract_syscall, but storage state updates immediately upon write. The protection pattern is checks-effects-interactions. The ReentrancyGuardComponent from OpenZeppelin Cairo provides ready-made protection. We use it rather than inventing our own.
Upgradability with replace_class_syscall
StarkNet provides a native upgrade mechanism: replace_class_syscall. A contract can replace its own class hash with a new one, while storage remains. This is similar to UUPS but without a separate proxy contract. Risks: if the new version changes the storage layout (variable order or names), data is interpreted incorrectly — in Cairo, storage addresses are computed from variable names. We utilize OpenZeppelin Cairo components for secure upgradability. OpenZeppelin provides UpgradeableComponent, which restricts the upgrade() call to the owner only. Before upgrading on mainnet, a mandatory test on a fork is required.
Our Process for Cairo Contract Development
- Analysis. We break down the requirements, determine which data goes into storage, which logic requires cross-contract calls (they are more expensive than internal ones), and whether upgradability is needed.
- Storage design. The most critical stage — an incorrect layout after deployment can only be fixed via an upgrade. Over 85% of audit issues are related to storage layout. Our expertise includes StarkNet upgradability patterns.
- Development. Cairo 2.8+, Scarb, OpenZeppelin Cairo. For DeFi logic, we study existing audited contracts (Ekubo, JediSwap). Deployment costs are 50% lower than in EVM. We also focus on Cairo gas optimization: profile VM steps and optimize loops and storage writes.
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Testing.
snforgeunit tests, fuzz testing, Katana for local integration, tests on Sepolia. Achieve coverage exceeding 95%. - Audit. The auditor ecosystem is smaller than for EVM, but teams like Trail of Bits, ChainSecurity, and Nethermind Security are active. We ensure every Cairo smart contract audit is thorough and 100% of our projects undergo audit before mainnet.
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Deployment. Declare + Deploy via
sncastorstarknet.js.
| Tool | Purpose | Status |
|---|---|---|
| snforge | Unit/integration tests | Actively developed |
| sncast | CLI for deployment | Stable |
| Katana | Local node | Actively developed |
| Voyager | Block explorer | Production |
| Service | Duration | Cost |
|---|---|---|
| Basic ERC-20 | 3-5 days | $5,000 |
| DeFi Protocol | 3-8 weeks | $15,000-$50,000 |
| Full Cycle with audit & mainnet | 2 months+ | Varies |
Timeline and Cost
Basic ERC-20 with custom logic — 3-5 days (starting at $5,000). DeFi protocol (AMM, lending) — 3-8 weeks ($15,000-$50,000). Full cycle with audit and mainnet deployment — from 2 months. The cost is determined after a technical briefing. Gas savings compared to EVM can reach 70% at high transaction volumes, leading to savings of hundreds of dollars per 10,000 transactions. For a typical DeFi protocol, our clients save on average $50,000 annually in gas costs compared to EVM.
Deliverables
- Architecture and storage layout documentation
- Source code with comments
- Unit tests (
snforge) and integration tests - Contract upgrade instructions
- Support for 2 weeks after deployment
- Consultation on mainnet launch
Contact us to discuss your project. We have completed over 20 projects on StarkNet and have 5+ years of experience in blockchain development. Get a consultation on migrating from Solidity to Cairo — we will help assess complexity and timelines.