The Purge

Remove Gas Refunds

Fast Sync

Remove Technical Debt

The STATE in Ethereum refers to the current information or status of all accounts and smart contracts, and is a representation of the CUMULATIVE outcomes of all transactions and smart contract executions up to the current block. It's dynamic and changes with every new block.

The HISTORY on Ethereum, on the other hand, refers to the record of all transactions and blocks that have been processed and confirmed on Ethereum since genesis. This includes details like transaction data, block headers, receipts, etc.. The history is essentially a log of how the chain has evolved over time and how the current state has been reached. It's a comprehensive record but is not directly required for processing new transactions.

History Expiry

State Expiry

Other Code Simplifications

In a sense, where History Expiry has a clear tradeoff in archiving old data that will become less accessible, State Expiry has the potential to be strictly positive, since it would only remove state trie nodes that have become obsolete.