Ethereum co-founder Vitalik Buterin has unveiled a proposal for an "Extremely Lean Chain" aimed at significantly reducing the state requirements of Ethereum's consensus chain. The proposal suggests shifting the responsibility to validators, who would manage their own state and submit daily STARK proofs, thereby eliminating the need for per-epoch processing and potentially accommodating millions of validators. Key features of the proposal include removing validator public keys from the on-chain state, storing only a deposit tree index, and canceling real-time reward and penalty processing. Validators would generate a STARK proof daily to update balances, achieving strong anonymity through ZK-STARK by re-randomizing validator identities daily. This approach could compress the per-validator state requirement from approximately 180 bytes to just 6 bytes, with daily proof processing achievable within an hour on standard hardware. The design also supports single secret leader election with minimal cost, enhancing Ethereum's scalability and efficiency.