Aave V3 Interest Rate Strategy

Implements the calculation of the interest rates depending on the reserve state. The model of interest rate is based on two slopes, one before the reserve’s optimal usage ratio and another from that point to 100%. Rates are set per reserve through PoolConfigurator.setReserveInterestRateData.

With utilization U and optimal usage ratio U_optimal, the variable borrow rate is:

R = \begin{cases} R_{base} + R_{slope1} \cdot \dfrac{U}{U_{optimal}} & U \le U_{optimal} \\ R_{base} + R_{slope1} + R_{slope2} \cdot \dfrac{U - U_{optimal}}{1 - U_{optimal}} & U > U_{optimal} \end{cases}

Interest Rates by Utilization

Each Aave market needs its own instance of this contract, because it caches the PoolAddressesProvider.

The source code is available on GitHub.

View Methods

getInterestRateData

Solidity

function getInterestRateData(address reserve) external view returns (InterestRateDataRay memory)

Returns the interest rate parameters of the specified reserve, in ray.

Input Parameters:

Name	Type	Description
reserve	`address`	The address of the reserve

Return Values:

Type	Description
`InterestRateDataRay`	`optimalUsageRatio`, `baseVariableBorrowRate`, `variableRateSlope1` and `variableRateSlope2`, all expressed in ray

getInterestRateDataBps

Solidity

function getInterestRateDataBps(address reserve) external view returns (InterestRateData memory)

Returns the interest rate parameters of the specified reserve, in bps.

Input Parameters:

Name	Type	Description
reserve	`address`	The address of the reserve

Return Values:

Type	Description
`InterestRateData`	`optimalUsageRatio`, `baseVariableBorrowRate`, `variableRateSlope1` and `variableRateSlope2`, all expressed in bps

getOptimalUsageRatio

Solidity

function getOptimalUsageRatio(address reserve) external view returns (uint256)

Returns the optimal usage ratio of the specified reserve.

Input Parameters:

Name	Type	Description
reserve	`address`	The address of the reserve

Return Values:

Type	Description
`uint256`	The optimal usage ratio, expressed in ray

getVariableRateSlope1

Solidity

function getVariableRateSlope1(address reserve) external view returns (uint256)

Returns the variable rate slope below the optimal usage ratio for the specified reserve. Applies while the usage ratio is below the optimal usage ratio.

Input Parameters:

Name	Type	Description
reserve	`address`	The address of the reserve

Return Values:

Type	Description
`uint256`	The variable rate slope, expressed in ray

getVariableRateSlope2

Solidity

function getVariableRateSlope2(address reserve) external view returns (uint256)

Returns the variable rate slope above the optimal usage ratio for the specified reserve. Applies while the usage ratio is above the optimal usage ratio.

Input Parameters:

Name	Type	Description
reserve	`address`	The address of the reserve

Return Values:

Type	Description
`uint256`	The variable rate slope, expressed in ray

getBaseVariableBorrowRate

Solidity

function getBaseVariableBorrowRate(address reserve) external view override returns (uint256)

Returns the base variable borrow rate for the specified reserve.

Input Parameters:

Name	Type	Description
reserve	`address`	The address of the reserve

Return Values:

Type	Description
`uint256`	The base variable borrow rate, expressed in ray

getMaxVariableBorrowRate

Solidity

function getMaxVariableBorrowRate(address reserve) external view override returns (uint256)

Returns the maximum variable borrow rate for the specified reserve.

Input Parameters:

Name	Type	Description
reserve	`address`	The address of the reserve

Return Values:

Type	Description
`uint256`	The maximum variable borrow rate, expressed in ray

calculateInterestRates

Solidity

function calculateInterestRates(
    DataTypes.CalculateInterestRatesParams memory params
) external view override returns (uint256, uint256)

Calculates the interest rates depending on the reserve’s state and configurations. This function returns only two values: the liquidity rate and the variable borrow rate.

Input Parameters:

Name	Type	Description
params	`DataTypes.CalculateInterestRatesParams`	The parameters needed to calculate interest rates

The DataTypes.CalculateInterestRatesParams struct is composed of the following fields:

Name	Type	Description
unbacked	`uint256`	The reserve deficit (field kept under its pre-V3.4 name); added to the denominator of the supply usage ratio
liquidityAdded	`uint256`	The liquidity added during the operation
liquidityTaken	`uint256`	The liquidity taken during the operation
totalDebt	`uint256`	The total borrowed from the reserve
reserveFactor	`uint256`	The reserve portion of the interest that goes to the treasury of the market
reserve	`address`	The address of the reserve
usingVirtualBalance	`bool`	Deprecated since Aave V3.4, always `true`
virtualUnderlyingBalance	`uint256`	The virtual balance of the underlying asset held by the reserve

Return Values:

Name	Type	Description
liquidityRate	`uint256`	The liquidity rate, expressed in ray
variableBorrowRate	`uint256`	The variable borrow rate, expressed in ray