Monad upgrade cuts clustered storage gas by 98%

Monad activated MIP-8 on mainnet at 14:30 UTC on Sept. 2 (Unix timestamp 1788359400) as part of the MonadTen revision. The upgrade replaces slot-level warming with storage pages of 128 slots for gas accounting.

A mainnet block measurement (block 101672712) recorded the new pricing pattern: an SLOAD at slot 0 charged 8,100 gas, a subsequent read on the same page charged 100 gas, and the first slot of the next page (slot 128) charged 8,100 gas again. Under the previous rules, adjacent untouched slots each incurred the full cold cost.

MIP-8 defines a storage page as 128 words of 32 bytes each, equal to 4,096 bytes. The first read anywhere on a page is billed 8,100 gas; additional SLOADs anywhere inside that warmed page cost 100 gas for the remainder of the transaction, until the call frame ends or a rollback occurs. Reads that cross page boundaries cause the full 8,100-gas cold charge at the first slot of the new page. Hashed or unaligned storage continues to be charged at the existing cold baseline.

Common Solidity storage layouts that place consecutive state variables, struct fields and array elements in adjacent slots can take advantage of the page-level pricing automatically. Mapping keys typically map to dispersed pages, but struct fields stored under a single mapping key remain contiguous and can share the cheaper reads inside a warmed page. The gas savings in any transaction depend on how many distinct pages the transaction touches and whether accesses are clustered within the same 128-slot range.

The specification maintains EVM execution semantics while changing assumptions used by developer tooling. EIP-2930 access-list entries now warm pages rather than individual slots. Storage-proof formats, gas-estimation tools and any code that assumes fixed per-slot SLOAD costs will need updates to reflect the page model. The upgrade also states that page warming is reversed if a call frame reverts.

Measured on-page read costs drop from 8,100 gas for the first access to 100 gas for subsequent accesses, producing roughly a 98% reduction in gas cost per slot for clustered reads after the initial page read.