# Ethereum's Fusaka Upgrade Just Hit Sepolia—Here's What It Means

Ethereum's major scaling push is moving into phase two. The Fusaka upgrade went live on Sepolia testnet this week, following Holesky's October 1 activation. This is the real stress test before hitting mainnet in December.

**What's Actually New**

Fusaka cranks Ethereum's block gas limit from 30M to 60M—doubling throughput. That means more transactions packed into each block and smoother handling of complex smart contracts. The network is now verifying if nodes can actually handle this doubled load without breaking.

The breakthrough here is **Peer Data Availability Sampling (PeerDAS)**. Instead of validators downloading entire blocks, they grab tiny data chunks from multiple peers to verify transactions. Faster, lighter, same security. Paul Harris from Consensys Teku confirmed it dramatically cuts storage requirements for validators—a real barrier to running full nodes.

**Timeline Reality Check**

- **Oct 28**: Final Hoodi testnet trial
- **December**: Mainnet launch

Gabriel Trintinalia flagged the core engineering challenge: ensuring 60M gas blocks run stable. Consensys Besu is specifically optimizing for this.

**Why This Matters**

Ethereum's been on an upgrade spree—Dencun cut gas fees 95%, The Merge cut energy costs 99%, Shanghai unlocked staking withdrawals. Fusaka is the next domino. Higher throughput = lower fees on mainnet, more room for DeFi, more competitive against Layer 2s.

Not financial advice, but this testnet phase tells you a lot about December's execution risk.