What is DeFi Yield?
In traditional banking, when you deposit money in a savings account, the bank lends that money to borrowers and pays you a small portion of the interest (typically 0.01–0.5% APY). The bank keeps the majority.
In DeFi (Decentralized Finance), lending and borrowing happens via smart contracts without the bank intermediary. Lenders deposit assets into a liquidity pool. Borrowers take loans from the pool and pay interest. The interest flows directly to the lenders.
Aave v3 is the leading DeFi lending protocol, operating on Polygon, Ethereum, Arbitrum, and other chains. In March 2026, USDC deposits on Aave Polygon earn approximately 4.5–6% APY — dramatically better than traditional bank rates.
Njangi House's optional yield feature deposits idle pool funds into Aave v3, earning this yield for the benefit of house members.
The Mechanics: How Pool Funds Work
A standard Njangi House round works like this:
- Round opens: Members begin contributing USDC
- Collection period: 4 weeks (for monthly frequency)
- Payout execution: When all members have paid, the pool is disbursed to the round recipient
During the collection period, there's a window where funds are "idle" — held in the contract but not yet disbursed. For a house with 6 members contributing 100 USDC each, the pool accumulates from $0 to $600 over the collection period, then sits at $600 until payout is executed.
Aave integration means this idle capital is put to work.
The Smart Contract Integration
The integration uses Aave's IPool interface with two key operations:
Supply (Deposit)
function _depositToAave(uint256 amount) internal {
usdc.forceApprove(aavePool, amount);
try IAavePool(aavePool).supply(
address(usdc),
amount,
address(this),
0 // referral code
) {
emit YieldDeposited(amount);
} catch {
// Silently continue if Aave unavailable
}
}
When a member contributes USDC (if yield is enabled), the contract immediately approves the Aave pool and calls supply(). The USDC leaves the house contract and enters the Aave liquidity pool. In return, the house contract receives aUSDC — Aave's interest-bearing token.
aTokens: The Key Mechanism
aUSDC (Aave USDC) is a 1:1 rebasing token. When you hold aUSDC, your balance increases automatically every second as interest accrues. If you deposit 100 USDC and the APY is 5%, after one year your aUSDC balance will be 105.
This is elegant: the house contract doesn't need to actively claim yield. It simply holds aUSDC, and the balance grows continuously.
Withdraw (Payout + Yield)
function _withdrawFromAave(uint256 amount) internal returns (uint256) {
try IAavePool(aavePool).withdraw(
address(usdc),
amount,
address(this)
) returns (uint256 withdrawn) {
emit YieldWithdrawn(amount, withdrawn > amount ? withdrawn - amount : 0);
return withdrawn;
} catch {
return amount;
}
}
When payout is executed, the contract withdraws from Aave. The withdraw() function returns the full balance including accrued yield. If the house deposited 600 USDC and accrued 2 USDC in yield during the collection period, the house receives 602 USDC back.
The extra 2 USDC is added to the payout — so the round recipient receives their full share plus a pro-rated share of the yield earned.
Yield Distribution Model
In the current implementation, all yield earned during a round is added to the payout for that round's recipient. This means:
- Early round recipients (Round 1, 2) receive less yield (shorter collection period)
- Later round recipients (Round 5, 6) receive more yield (full collection period)
A future governance proposal will introduce yield pooling — where yield from all rounds is accumulated and distributed equally to all members at the end of the full cycle. This creates a fairer distribution and slightly increases the incentive for members in later payout positions.
Risk Analysis
No DeFi integration is risk-free. We're transparent about the risks:
Protocol risk: Aave v3 is a battle-tested protocol with billions in TVL, multiple audits, and years of mainnet operation. However, no smart contract is 100% risk-free. An exploit in Aave could, in theory, affect deposited funds.
Our mitigation: Yield integration is opt-in. It must be explicitly enabled when creating a house. The majority of houses should run without yield integration. For yield-enabled houses, we recommend smaller contribution amounts to limit exposure.
Liquidity risk: Aave withdrawals can theoretically fail if the pool's utilization rate is extremely high (all available USDC is borrowed out). In practice, USDC pools on Polygon maintain >20% liquidity reserve.
Our mitigation: The try/catch wrapper in our smart contract means that if an Aave withdrawal fails, the transaction does not revert — the contract falls back to paying the payout from its direct USDC balance. Yield is lost, but principal is protected.
Oracle/rate risk: The APY on Aave fluctuates based on market demand. During low-utilization periods, APY can drop to 1–2%.
Our mitigation: Yield is a bonus, not a core promise. House contribution amounts and payout expectations are set without reference to yield. Any yield earned is additional.
Real Numbers: What to Expect
At 5% APY on Aave Polygon:
- Monthly collection period: 30 days
- Pool size: $600 USDC (6 members × $100)
- Average deployed duration: 15 days (accumulates from $0 to $600)
- Average deployed balance: $300
- Yield earned: $300 × 5% × (15/365) ≈ $0.62
At the scale of a typical house, yield contribution is small — a few cents to a few dollars per round. But across thousands of houses and larger contribution amounts, it adds up. And for members contributing hundreds of USDC monthly, the yield compounds meaningfully.
The bigger benefit is philosophical: by connecting African community savings to DeFi infrastructure, we're demonstrating that these communities have access to the same financial tools as anyone in the world.
Enabling Yield for Your House
Yield integration is enabled at house creation and cannot be changed after deployment (to ensure all members know the rules when they join).
In the Create House wizard, Step 4 includes:
- Toggle: "Enable Aave yield on idle funds"
- Info tooltip explaining the mechanics and risks
- Warning: "Yield integration adds smart contract risk. Only enable if your members understand and accept this risk."
We recommend yield integration for experienced groups who are comfortable with DeFi. For first-time users, we recommend starting without yield and enabling it in a future house once comfortable with the platform.
Learn more about our security practices or create a yield-enabled house.