# Variables should be cached to memory to save gas Low/Info · Three Sigma · Omnichain RWA tokenisation · 6th April, 2024 Finding 3S-MZ-N01 of the MetaZero Staking security review. - Protocol: https://metazero.gg/ - Report: /reports/metazero-ii - Codebase: https://github.com/0xsimao/stakingContract/tree/dffac73e838a9fbd12bed18e41b9799177bcde7f - Source: https://cdn.sanity.io/files/qoqld077/production/3e07b0c2806b62578b8031e88c59bc5dbd38de1b.pdf --- ### Description Storage reads are expensive and should be avoided. This is usually done by caching storage variables in memory ones. ### Recommendation Replace all storage rewards that happen more than once per function (or even better, per flow) for memory caching. Example: ```solidity function rewardPerToken() public view returns (uint256) { uint256 totalStakedAccruingRewardsCached = totalStakedAccruingRewards; if (totalStakedAccruingRewardsCached == 0) { return rewardPerTokenStored; } return rewardPerTokenStored + ( ``` (lastApplicableTime() - lastUpdateTime) * rewardRate * 1e18 / totalStakedAccruingRewardsCached ```solidity ); } ``` ### Status Acknowledged --- Related findings: - [Storage variables should be cached whenever possible to save gas](https://0xsimao.com/findings/glacier-storage-cached-whenever-gas): Glacier - [Storage variables can be cached to save gas](https://0xsimao.com/findings/mitosis-storage-variables-cached-gas): Mitosis - [Storage variables can be cached to save gas](https://0xsimao.com/findings/orange-storage-variables-cached-gas): Orange Bridge - [pool-v2-private: cache list length in memory and uncheck i_ to save gas.](https://0xsimao.com/findings/maple-finance-iii-private-cache-uncheck-gas): Maple Finance