Do rollups actually scale Ethereum or are we fooling ourselves?

In the quest to scale Ethereum, developers have been busily building mechanisms called “rollups” that operate more efficiently “on top” of the base chain.

But what exactly is a rollup? When asked the loaded question, Jon Charbonneau laughs.

“Oh, this is gonna be tough,” he says. “This has been, like, a whole big debate with everyone over the last few months.”

It’s important to get the mental model right, he says, in order to determine the true purpose of a rollup — and whether it’s a genuine scaling solution for Ethereum. After all, if it’s just building “on top” of the chain, is it really scaling the chain?

On the Lightspeed podcast (Spotify/Apple), the co-founder and partner at crypto investment firm DBA gives a simple definition before elaborating: “A rollup is just some state that you derive off of some data, basically, that is posted on another blockchain, another data layer.”

“So there’s data posted on Ethereum and I can run some state transition function over that data that says, ‘Hey, this is the state of my rollup.’”

“That is all you really need to have a rollup at a fundamental level.” Everything else, while important, is just a matter of implementation, he says.

The concept can get a little more convoluted when it comes to bridging — or not — back to Ethereum, Charbonneau explains. “If it lacks this bridge from the base layer to the rollup, well, then what the hell is the point of this thing?”

The researcher notes that a rollup doesn’t necessarily have to bridge back to the original data layer if it is strictly using the base network for its security properties. He suggests that a developer might decide to use another chain’s consensus and other security benefits instead of bootstrapping their own validators, for example, allowing for a much easier setup.

But the use cases for such a rollup are “unclear,” Charbonneau says. “You want to be able to bridge assets around,” he says. “That is what we are using most of these things for.”

Defining scaling

The discussion centers on the question: Do rollups actually contribute to scaling Ethereum or are they ultimately just offloading the activity elsewhere?

The crux of the matter is the meaning of “scaling,” Charbonneau explains. He defines it as “trying to get more throughput through a system relative to whatever the resource requirements are.”

With rollups, he says “it’s possible to create more efficient execution environments that, for comparable amounts of resources, do get you a lot more throughput.”

In regards to the question of whether rollups actually scale Ethereum, Charbonneau admits he doesn’t have “the perfect answer.”

The answer lies within a “fuzzy line,” he says, “which is why a lot of people very reasonably say, ‘okay, rollups aren’t scaling Ethereum — you just have to consider the base layer itself.’”

“You’re generally scaling it if you are using the properties of the underlying system in some way and retaining a lot of the underlying security properties of the system.”

Scaling with rollups on Ethereum “lets you do a lot more interesting things with your [ether] [ETH] that you couldn’t do on the base layer,” he says.

“If I send my [ETH] to Coinbase, and now I can do whatever I want with Coinbase, that’s not really scaling in my mind at that point,” he says, “because you effectively just have no security properties derived from it.”

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