Roll ups have become the dominant scaling solution, praised for inheriting Ethereums security while dramatically increasing throughput. But beneath the surface lies a cost that's rarely discussed: the burden of data availability. Every rollup transaction, even though executed off-chain, must have its data published to Ethereum for anyone to reconstruct the current state. This data gets permanently etched into the blockchain, bloating its size and creating ongoing costs that users pay with every transaction.

When you make a swap on a rollup, the details of that transaction—the amounts, addresses, signatures—all get compressed and posted to Ethereum as call data. This is necessary because roll ups achieve their security by allowing anyone to verify the rollup operator's work. If the data weren't available, nobody could check whether the operator processed transactions correctly or could reconstruct the state to submit fraud proofs. The result is that while roll ups batch hundreds of transactions into single proofs, reducing computational verification costs, they still consume ETH precious block space with data.

The economics become problematic at scale. As roll ups grow and more users transact, the data they publish competes for the same limited Ethereum block space. During periods of high activity, this pushes up the cost of data availability, which gets passed directly to rollup users through higher fees. Even with innovations like EIP-4844's blob space, which provides cheaper temporary data availability, the fundamental issue remains: every transaction carries a data footprint that must be paid for and stored, at least temporarily, on the main chain.

Plasma sidesteps this entirely through a clever inversion of the security model. Instead of publishing all transaction data to Ethereum, Plasma operators only publish periodic commitments and small cryptographic fingerprints of the current state. @Plasma #Plasma $XPL