No More Waiting: Ethereum Finally Cracked Realtime Execution with 100ms Sub-Blocks

Ethereum has officially HIT a performance milestone that many believed was years away. For the first time ever, a mainnet block was broken down into synthetic sub blocks just 100 milliseconds apart. ETHGas and collaborating teams successfully executed 44 of these “realtime blocks” inside a single twelve-second Ethereum block, updating state continuously and allowing transactions to settle in near-instant intervals. This effectively brings millisecond-level execution to the Layer 1 network.

We’ve split the atom(!) and enter a new era breaking Ethereum blocks down into synthetic 100ms sub-blocks on mainnet. These ‘Realtime Blocks’ were the result of many teams working tirelessly, and independently, to make Ethereum better. This new era, the realtime era, is a…

— ETHGAS (@ETHGasOfficial) November 16, 2025

How We Reached This Moment

Anyone following Ethereum’s research threads might recall how certain ideas kept resurfacing. Researchers discussed preconfirmations. Builders experimented with new blockspace markets. Teams explored whether block ordering could be guaranteed without sacrificing openness. Individually, each effort looked ambitious but isolated. Put together, they were all pointing toward the same outcome: reducing the time it takes for Ethereum to acknowledge what users want to do.

Around late 2024 and early 2025, this trend became more visible. ETHGas began studying how blockspace could be reserved or traded before a block was built. The idea was simple: if users could secure blockspace ahead of time, they could bypass unpredictable mempool competition. At the same time, other groups were going deeper into preconfirmations: techniques that allow builders to give users a binding, economically secured promise about the order of their transactions.

The Pieces Start Fitting Together

The breakthrough came when teams began combining their approaches. ETHGas used its marketplace to secure blockspace in advance, while builders integrated Flashbots’ flashblocks system to simulate and execute transactions with unprecedented speed. They experimented with multiple techniques and what emerged was a functioning realtime pipeline inside Ethereum’s existing structure. Instead of one block executed at the end of twelve seconds, the system could now produce dozens of miniature updates inside the same time window. Each update carried forward state changes, meaning a user could take multiple actions: buy, sell, adjust positions, all within a single block and still trust that ordering would be preserved.

The economic layer made this even more meaningful. If a validator committed to producing realtime blocks and then failed, they could be slashed. Collateral posted in ETH or restaked via EigenLayer acted as the enforcement mechanism. This transformed a technical idea into a reliable & accountable system.

What This Means for Ethereum

The result is a version of Ethereum that behaves differently from any point in its history. It now has the ability to process actions at speeds comparable to high-performance chains while preserving the decentralization that defines it. Developers can build applications that react faster. Traders can execute strategies within a single block. Everyday users may eventually experience Ethereum as something far more responsive than they are used to.