How to build a custom lending protocol on a Compound fork?
We develop custom lending protocols on a Compound fork. Our experience: 5+ years in DeFi and 20+ deployments. At first glance, "making a fork" sounds simple: copy the repository, change parameters, deploy. In practice, it's the source of most hacks in the lending category: incorrect exchange rate calculation, broken liquidation incentive logic, a single oracle price source. We break down what you actually need to do to make a Compound fork work correctly.
What usually breaks when forking Compound
Exchange rate and accumulated interest
Compound uses the cToken concept: a user deposits DAI, receives cDAI. Over time, the exchange rate increases due to accrued interest from borrowers. The rate calculation goes through accrueInterest(), which must be called before any balance operation.
A common mistake in forks: accrueInterest() is not called everywhere needed—for example, it's omitted in a custom liquidation function. Result: exchange rate becomes stale, users see incorrect balances, or the liquidator receives less collateral than they should. In one known fork, this led to bad debt accumulation unnoticed for weeks.
Check: in tests, explicitly call vm.roll(block + N) and verify that exchangeRateCurrent() correctly increases proportionally to borrowRate and time.
Collateral factor vs liquidation threshold
In Compound V2, collateralFactor serves two roles: it determines how much can be borrowed and sets the liquidation threshold. This means a position goes into liquidation almost immediately upon crossing the borrow limit—there is no buffer between max borrow and liquidation. Aave V3 addressed this by separating LTV (loan-to-value, how much can be borrowed) and liquidationThreshold (when to liquidate). A buffer of 10-15% gives the borrower time to add collateral.
If you're building a fork for production with real users—we recommend adding this separation. It doesn't change the core math of Compound, but it significantly improves UX and reduces unnecessary liquidations during short-term volatility.
Oracle: a single Chainlink feed is insufficient
Compound V2 uses Chainlink as the sole price source. If the Chainlink feed hangs for some reason (and it happens—feeds for less liquid assets may not update for hours), the protocol operates with stale prices. In high volatility, this creates either arbitrage opportunities or bad debt risk.
Minimum protection: check the updatedAt timestamp from Chainlink and block operations if data is older than N seconds. Extended protection: a secondary oracle (e.g., Uniswap V3 TWAP as fallback) with a circuit breaker—if the two oracle prices diverge by more than X%, operations are paused.
What we customize in the fork
Typical customizations for a specific project:
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List of supported assets. Compound supports major assets—ETH, WBTC, USDC, DAI. If you need lending for niche tokens (LST, LP tokens, RWA), we add new markets with individual risk parameters. LP tokens as collateral require separate valuation logic via underlying assets.
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Interest rate model. Compound uses JumpRateModel: low rate at low utilization, steep increase after the kink-point (usually 80%). For stablecoin pools, kink can be higher (90%); for volatile assets, lower (60%). We set parameters (baseRate, multiplier, jumpMultiplier, kink) to fit the specific tokenomics.
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Governance and admin functions. Compound V2 has a single admin address with broad rights. For a production protocol, minimum: Gnosis Safe multisig for admin, timelock on critical changes (risk parameters, oracle, pause guardian). Decentralized governance via Governor Bravo can be added later.
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Isolation mode. Compound V2 does not isolate risk between assets—a problem with one token can affect the entire protocol. Compound V3 (Comet) addressed this radically by introducing single-collateral markets. For a fork, we recommend at least basic isolation: separate pools for high-risk assets.
Why forking Compound isn't just a copy?
A fork without customization is a copy with someone else's bugs. Compound V2 lags behind Aave V3 in UX due to the lack of a liquidation buffer, but our customization bridges that gap. We add isolated pools, fallback oracle, and flexible risk parameters to make the protocol more secure and user-friendly.
Stack and process
Base: the compound-protocol repository or compound-v2-subgraph for The Graph indexing. Development in Foundry: unit tests for each market, integration tests with mainnet fork to verify oracle integration.
Auditing is mandatory. Forking Compound does not mean "automatically safe"—customizations create new vectors. We recommend Code4rena or Sherlock contest for broad auditor coverage at a fixed budget.
What's included in the work
- Requirements analysis and architecture design
- Smart contract development and customization
- Unit and integration tests (coverage >90%)
- Internal audit with Slither, Echidna, manual review
- Testnet and mainnet deployment
- Integration with Gnosis Safe, timelock, subgraph
- Technical documentation and client team training
Estimated timelines
| Stage |
Duration |
Content |
| Design |
1-2 weeks |
Risk parameters, asset list, governance model |
| Development |
4-8 weeks |
Contracts, customizations, tests |
| Internal audit |
1-2 weeks |
Slither, Echidna, manual review |
| External audit |
2-4 weeks |
Mandatory before mainnet |
| Deployment & monitoring |
1 week |
Gnosis Safe, subgraph, dashboard |
Basic fork with minimal parameter changes: 4-6 weeks development. Fork with significant customizations (new interest rate model, isolation pools, custom oracle): 8-12 weeks. Audit runs parallel to the last weeks of development, but the final code must be frozen two weeks before audit starts.
Comparison: Compound V2 vs custom fork
| Feature |
Compound V2 |
Our custom fork |
| Liquidation buffer |
No |
10-15% (LTV vs liquidationThreshold) |
| Oracle |
Chainlink solo |
Chainlink + Uniswap V3 TWAP fallback |
| Governance |
Single admin |
Multisig + timelock (until full DAO) |
| Risk isolation |
No |
Basic isolation pools |
Ready to discuss your project? Contact us for a consultation. Order turnkey development and get a reliable lending protocol with quality assurance.
DeFi Protocol Development
We design modular DeFi protocols where the math of stablecoins, liquidity, and oracles works flawlessly. Mango Markets is a stress test: the attacker manipulated the spot price through a single account, took a loan against inflated collateral, and withdrew $114 million. The oracle took the price from a single source without TWAP. Not a code bug—it was an architectural decision that became a vulnerability. Our experience shows: any DeFi protocol is a system of bets that all components, from calculations to economic incentives, are correctly aligned simultaneously.
We don't write code under the 'if it works, don't touch it' mindset. We model stress scenarios: cascading liquidations, depegs, flash loans. Only then do we build events that won't break the protocol.
Why are oracles a critical component of DeFi?
Most major DeFi hacks started with oracle manipulation. Let's break down the three layers we use in every project.
Spot price as oracle—not an option. Uniswap v2 spot price can be shifted by a flash loan in one transaction. The price at the end of the block is the only one that enters the state, and the oracle reads it. Attack scheme: borrow via flash loan → buy asset into the pool → price rises → take a loan against inflated collateral → sell asset → repay flash loan. One transaction.
TWAP as protection. Uniswap v3 observe() averages the price over a period (30 minutes). Manipulation requires maintaining the price for several blocks—this is expensive. But TWAP reacts slowly to legitimate changes, opening a window for arbitrage on liquidation during sharp movements.
Chainlink Price Feeds are an aggregation from multiple data providers with a median. Standard for lending. Problem: heartbeat 1–24 hours and deviation threshold 0.5%. If the price doesn't move, the feed may not update for a day. In volatile markets—lag.
| Oracle |
Mechanism |
Manipulation Protection |
Latency |
| Chainlink |
Median from independent providers |
High (decentralization) |
Up to 24h at 0% movement |
| Uniswap v3 TWAP |
Average price over N blocks |
High (hard to maintain) |
30 min – 1 h |
| Pyth Network |
Cross-chain low-latency |
Medium (dependent on publisher) |
Seconds |
In production, we use a two-tier check: Chainlink aggregator + Uniswap v3 TWAP as a verifier. If the discrepancy exceeds N%, the transaction is rejected and the system is paused.
How to protect a DeFi protocol from flash loan attacks?
Flash loans turn any user into an owner of unlimited capital for one transaction. Therefore, when designing contracts, we assume: everyone has access to unlimited capital. This completely changes the threat model.
Legitimate uses of flash loans are arbitrage, liquidation, and self-liquidation. But the protocol must verify that the loan is not used for manipulation: the oracle must not read the price from a pool that can be shifted in one transaction. We add checks on block.timestamp and minimum liquidity depth.
Key Components of DeFi Architecture
| Protocol Type |
Core Mechanism |
Main Risk |
| DEX (AMM) |
x*y=k or concentrated liquidity |
impermanent loss, oracle manipulation |
| Lending |
collateral ratio, liquidation |
bad debt during cascading liquidations |
| Yield aggregator |
auto-compounding strategies |
rug via strategy upgrade |
| Derivatives / Perps |
funding rate, mark price |
liquidation cascades, socialized losses |
| Liquid staking |
stETH-style rebasing |
depegging on mass unstake |
AMM: From x*y=k to Concentrated Liquidity
Uniswap v2 uses x * y = k. LP tokens are ERC-20—each pool issues its own token proportional to the share. Problem: liquidity is spread across the entire curve, most of it unused.
Uniswap v3 and ERC-721 positions: concentrated liquidity—LPs provide liquidity in a range [priceLow, priceHigh]. Capital efficiency up to 4000x for stable pairs. But ERC-721 breaks vault strategies built for ERC-20. Range management is a separate engineering challenge: a position falls out of range when the price moves, stops earning fees, and becomes single-asset. Protocols like Arrakis Finance automatically rebalance. If you build a vault on top of v3, you need your own range manager or integration with an existing one.
Slippage in v3 is calculated via sqrtPriceX96—96-bit fixed-point math. Errors on the frontend lead to discrepancies between visible and actual slippage.
Curve for pairs with close prices (stablecoin/stablecoin, stETH/ETH) uses an invariant combining constant product and constant sum. Lower slippage within the peg range. Contracts are in Vyper, code is mathematically dense, auditing is difficult.
Lending Protocols: Collateral, Liquidation, Bad Debt
LTV defines the maximum loan against collateral. Liquidation threshold is the level for liquidation. The difference is the buffer for the liquidator. Typical example: LTV 75%, liquidation threshold 80%, bonus 5%. If the price drops 20%+, the position is open for liquidation.
Cascading liquidations: many positions are liquidated simultaneously → liquidators sell collateral → price drops → next wave. LUNA/UST 2022 is a classic cascade.
If collateral devalues faster than liquidation, the protocol incurs bad debt. Aave uses a Safety Module (staked AAVE), Compound uses reserves. Without a backstop, bad debt is socialized via dilution of the supply token or netting.
Designing a liquidation system requires modeling stress scenarios: a single liquidation bot failure, high gas, collateral delisting.
Yield Farming and Incentive Mechanics
Liquidity mining distributes governance tokens to LP providers. Problem: mercenary capital—farmers come, sell tokens, leave. TVL is illusory.
Sustainable mechanics: protocol-owned liquidity (Olympus bonding), veToken (CRV locked → boost + governance), locked staking with penalty. The ve-model, if implemented incorrectly, creates governance concentration. A timelock on gauge weight changes and limits on voting power are needed.
What Our DeFi Protocol Development Includes
- Architectural documentation: contract interaction diagrams, liquidation stress tests, oracle calculations.
- Implementation in Solidity 0.8.x with OpenZeppelin 5.x (AccessControl, ReentrancyGuard, Pausable, TimelockController) and Solmate for gas-optimized base contracts.
- Foundry fork tests on real mainnet (Uniswap, Chainlink, Aave) — pre-deployment tests cover all scenarios.
- Audit: at least two independent auditors for TVL over $1M. Code4rena or Sherlock for bug bounty.
- Deployment with Gnosis Safe 3/5 multisig + timelock 48–72 hours.
- Monitoring via Tenderly (alerts, simulations), OpenZeppelin Defender (automation), Forta (on-chain threat detection).
- Post-launch support: updates, patches, upgrades via proxy.
Our Expertise and Experience
We have been developing DeFi protocols since 2020, delivering 30+ projects with a combined TVL of over $150 million. Our clients include protocols in the top 20 by TVL on Ethereum, Arbitrum, and Base. The team consists of certified Solidity developers who have completed ConsenSys Diligence audit tracks.
DeFi basic principles that we apply in practice.
Timelines
- DEX with AMM (Uniswap v2 fork): 6–10 weeks
- Lending protocol (Aave-style, single collateral): 3–5 months
- Yield aggregator with multiple strategies: 2–4 months
- Full-fledged DeFi protocol with governance: 5–8 months including audit
Cost is calculated individually—contact us for a project estimate.
Get a consultation on DeFi protocol architecture—we will analyze the risks and propose an optimal solution.
