The amount of resources Ethereum needs to maintain itself is rising by the day and, at a certain point, that burden will increase to infinity, causing serious problems for the network's stability.
Technically, Ethereum is the World Computer, a platform that exists with the support of thousands of nodes. The node system is what makes Ethereum the network we know: nodes provide the hardware, EVM provides the virtual computer and the blockchain records every transaction made in Ether's history.
(1/20) @ethereum Roadmap: State Expiry
— Haym (@SalomonCrypto) November 3, 2022
As the World Computer attracts more use, the amount of resources needed to keep itself running increases. Today, that burden will increase to infinity, eventually crushing the network.
A roadmap to a sustainable Ethereum. pic.twitter.com/LNfEakxE2F
The virtual machine is stored in a data structure called a Merkle tree. Its main use is to verify data stored, handled and transferred between computers. Merkle trees ensure the authenticity of data received from other peers on the network.
However, there are some downsides, the most problematic one being scaling. As of today, the World Computer stores the entire EVM, including every entry, account and address going back to its genesis. While storing that amount of data is not causing problems today, it will become a problem in the future, growing to infinity. Luckily, there is a solution called "state expiry."
With state expiry, parts of the state default become inactive and must be renewed by "touching," which is essentially accessing the state that will defer expiry. Thanks to the mechanism, the size of the EVM's state will remain reasonable and make room for new objects.
While the offer to solve existing Merkle tree scaling issues sounds good on paper, implementing it would be a complicated process that would take a lot of time and manpower. However, the most recent transition to PoS proved that anything is possible with Ether.