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GeneralOverview
Findings
Medium (2)
DiscussionUse of APR in configurationLiquidate maximum percentage is weightedDesync between reserve and obligation interest
Threat ModelWhat are threat models?1-lending_market3-reserve4-obligation
Audit ResultsSummary

Use of APR in configuration

The following formula is used for the per-second APR.

The per-second interest rate is calculated by dividing the yearly APR by the number of seconds in the year and adding one. The formula for an exact per-second interest rate from an annual interest rate uses a k-th root where k is the number of seconds in a year. This can lead to discrepancy between APR and the effective interest paid (i.e. the APY).

In the below graph, we have graphed the discrepancy over a year in the exact interest rate and APR. For clarification, the difference is the extra interest paid using the APR formula over an exact interest rate formula.

Graph showing the interest discrepancy

This doesn't cause any issues, as it is mainly how the APR is represented and will be used in the protocol. We would recommend the suilend team to display both the APR (and expected APY calculated based on that) in the frontend so users are aware of this difference.

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