Smart Contract Refactoring
The contract works, funds aren't lost — but each new feature triggers panic. Storage layout has bloated, functions are 200 lines long, and tests are absent. Our experience shows that such technical debt accumulates unnoticed until it leads to critical failures or gas waste. We guarantee: after refactoring, the code becomes predictable and secure.
Where Technical Debt Hides Most Often
Suboptimal Storage Layout
Solidity packs variables into 32-byte slots. If variables are declared in the order uint128, uint256, uint128, that's three slots instead of two. On a contract with thousands of calls per day, reordering 8 variables for slot packing reduced gas on write operations by 40%. Savings — up to $5000 per year per user. That's real money going to gas.
Unbounded Loops as Gas Griefing
The pattern for (uint i = 0; i < users.length; i++) in a contract where users can grow is not just inefficient. An attacker adds 10,000 addresses, and a call to distribute() exceeds the block gas limit (30M gas). The function becomes unexecutable — contract stuck. Refactoring to a pull pattern with pagination solves this structurally.
Cross-Function Reentrancy
OpenZeppelin's ReentrancyGuard protects one function. But if withdraw() is guarded and claim() is not — and both modify the same balance mapping — reentrancy is possible. This is how an $80M exploit worked. During refactoring, we audit the entire call graph, not just individual functions.
How We Approach Refactoring
The first step is static analysis with Slither. In 2-3 minutes, it finds reentrancy, uninitialized variables, tx.origin authorization, and shadow variables. Slither gives hundreds of warnings — critical ones must be separated from informational. Then, Mythril for symbolic execution on key functions.
Here is the step-by-step process:
- Analysis: static and symbolic analysis (Slither, Mythril), compile a prioritized issue registry.
- Planning: group changes, isolate dependencies, write tests for edge cases.
- Refactoring: each change in a separate PR with tests. Apply Solidity best practices, Check-Effects-Interactions, Diamond pattern (EIP-2535).
- Testing: fuzz tests in Foundry, compare gas reports with
forge snapshot. - Deployment: scripts on ethers.js, monitoring via Tenderly.
Example: Staking Pool Refactoring
On one project, we replaced an unbounded loop with a pull pattern with pagination. Added an emergencyWithdraw flag for safe exit under DoS. Implemented custom errors instead of string require — saving 100 gas per revert. Result: the distribute function became executable even with 50,000 users, and overall gas savings reached 15%.
Why Smart Contract Refactoring Is Cheaper Than an Audit?
An audit identifies issues but doesn't fix them. Refactoring eliminates technical debt immediately. We don't just write a report — we rewrite the code to be secure and gas-efficient. A typical audit costs $10-30k, and refactoring with fixes costs the same, but with working code. Contact us — we will assess your project and propose a work plan.
Gas Optimization: Specific Numbers
| Pattern | Gas Savings (Approx.) |
|---|---|
| Slot packing variables | 20-40% on SSTORE |
| memory instead of storage in functions | 15-30% on reads |
| unchecked increment | 60-80 gas per iteration |
| calldata instead of memory | 50-100 gas per argument |
| Custom errors instead of require strings | 50-200 gas per revert |
Typical Issues and Solutions
| Issue | Solution | Savings/Benefit |
|---|---|---|
| Reentrancy across multiple functions | Full call graph analysis + OpenZeppelin ReentrancyGuard | Prevents losses up to $80M |
| Suboptimal storage layout | Variable reordering, packing | $5000/year gas savings |
| Unbounded loops | Pull pattern with pagination | Guaranteed function executability |
What Is Included in the Work
- Code audit with vulnerability registry and optimization opportunities.
- Fixing all critical and medium issues.
- Tests in Foundry (unit, integration, fuzz).
- Gas report comparison before/after.
- Documentation of changes and deployment instructions.
- Code warranty — 6 months support.
What Mistakes Are Most Often Made During Refactoring?
- Fix only obvious issues without checking cross-function reentrancy.
- Change ABI without isolation — break integrations.
- Forget to update tests after changes.
- Simplify storage layout but ignore inherited contracts.
Our engineers have 10+ years of blockchain development experience and have completed over 50 refactoring projects. Get a consultation — we'll tell you what needs fixing in your contract.
Solidity Version Upgrade
Migrating from 0.6/0.7 to 0.8+ includes: automatic overflow checks (SafeMath no longer needed), custom errors, and immutable variables. But it's not just changing the pragma — ABI encoding changes, assembly patterns require adaptation. We test each change in isolation.
OpenZeppelin ReentrancyGuard is the security standard we use as baseline. Contact us — we will assess your project and offer turnkey refactoring.