Partnering with 10 node operators to decentralize Espresso’s Cappuccino testnet

Espresso Systems
3 min readApr 12, 2024

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Espresso will be decentralizing the set of nodes running HotShot consensus in its upcoming testnet, Cappuccino, to be released later this month. This is an important milestone on Espresso’s journey of steadily growing the operator set leading up to mainnet — with HotShot’s ultimate goal being to encompass the distribution and staked capital of the entire Ethereum validator set.

In our latest testnet, Gibraltar, we partnered with Blockdaemon, which ran 4 HotShot nodes across Asia and Europe, in addition to those operated by Espresso Systems. With Blockdaemon’s support, Espresso was the first platform for rollup sequencing running with external node operators on testnet.

Deploying Espresso testnets on multiple nodes run by a diverse group of node operators is an important step towards readying the Espresso infrastructure for a production launch. As part of this, our next testnet, Cappuccino, will be run on 100 nodes that are geographically distributed across 6 continents.

Decentralizing HotShot for the Cappuccino testnet

Espresso has two core components. The first is a sequencing marketplace, where rollups sell slots to participating sequencers. The second is a consensus protocol that functions as a finality layer. The finality layer supports the marketplace and can also be leveraged independently.

A sequencer participating in the Espresso marketplace may bid for the opportunity to sequence blocks for multiple rollups at once — allowing them to facilitate cross-rollup activity, among other advantages. A rollup may have a default sequencer, which produces blocks for the rollup in the event that the sequencing opportunity isn’t sold. The marketplace maximizes economic efficiency within the entire rollup sequencing space and the value that rollups are able to capture..

The finality layer of Espresso is powered by HotShot. This is a BFT consensus protocol that provides users (or external entities including bridges, exchanges, etc.) with fast preconfirmations, or assurances that transactions will not be reversed, and will eventually be reflected on the Ethereum L1. HotShot is an optimistically responsive network, which means it can produce blocks as quickly as the network allows and reach finality within seconds, while scaling to thousands of operators. Expanding and diversifying the HotShot operator set in Cappuccino will help us continue to push the envelope on Espresso’s performance and security.

How we selected partner node operators

In February, we announced an open application process for node operators interested in running HotShot nodes for the Cappuccino testnet. After engaging with over 600 node operators, we were able to select 10 operators who will be running HotShot nodes for Cappuccino: Blockdaemon, Figment, Informal Systems, KudasaiJP, LinkPool, Nethermind, P2P.org, Sub7, Unit 410, and ZKValidator.

In this selection process, we prioritized operators in a range of locations to improve geographical diversity of the network and could support several cloud and bare metal environments. We also decided to work with experienced and highly technical operators who will help us to further define our node operator onboarding process and industry best practices. This is crucial as we look to create a smooth onboarding process for future operators, including those who join the HotShot network when it becomes fully permissionless.

These Cappuccino operators will collectively run 100 HotShot nodes for the testnet, spanning six continents.

Future plans towards permissionlessness

With Cappuccino, Espresso will be the first platform for shared sequencing run on a distributed set of over 100 nodes. This paves the way to a credibly neutral decentralized network that will support rollup interoperability and security, while maintaining high performance.

We’re looking forward to running the Cappuccino testnet with our partners and building the supporting infrastructure to create a united Ethereum. If you’re a rollup interested in deploying on Espresso, please get in touch with us here.

We’re grateful for the time and effort contributed by our partners in support of the Cappuccino testnet, especially those who participated in the open call for node operators. Please note that although we will not be able to respond to all applicants individually, we will share progress updates and selection decisions via Twitter/X and in our Discord server via the #node-operators-updates channel. We will continue to update the recommended technical specifications for running a node in our documentation.

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Espresso Systems
Espresso Systems

Written by Espresso Systems

We are the lead developers of the Espresso Sequencer, which supports rollups with decentralization, scale, and interoperability.

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