Gas Optimizations

[code423n4]

[Gas - 01] - Useless variable

https://github.com/Plex-Engineer/lending-market-v2/blob/ea5840de72eab58bec837bb51986ac73712fcfde/contracts/ERC20.sol#L13

_initialSupply is not used anywhere so could be removed.

[Gas - 02] Use Custom Errors

Instead of using error strings, to reduce deployment and runtime cost, you should use Custom Errors: see https://blog.soliditylang.org/2021/04/21/custom-errors/. This would save both deployment and runtime cost.

Examples:
https://github.com/Plex-Engineer/lending-market-v2/blob/ea5840de72eab58bec837bb51986ac73712fcfde/contracts/Stableswap/BaseV1-periphery.sol#L104
https://github.com/Plex-Engineer/lending-market-v2/blob/ea5840de72eab58bec837bb51986ac73712fcfde/contracts/Stableswap/BaseV1-periphery.sol#L106

[Gas - 03] Using address to test equality would be more efficient

Instead of doing https://github.com/Plex-Engineer/lending-market-v2/blob/ea5840de72eab58bec837bb51986ac73712fcfde/contracts/Stableswap/BaseV1-periphery.sol#L495 or https://github.com/Plex-Engineer/lending-market-v2/blob/ea5840de72eab58bec837bb51986ac73712fcfde/contracts/Stableswap/BaseV1-periphery.sol#L500, it’d be more efficient to have setters and test that addresses are the same as it would avoid an external call.

[GalloDaSballo]

[Gas - 03] Using address to test equality would be more efficient

100 gas from the CALL also another 2.1k here, another 200 for the second CALL + SLOAD.
Rest is negligible

I recommend focusing on immutables to keep it short and get additional savings