Cortado Testnet Integrates with OP Stack

Espresso Systems releases testnet 3 (Cortado), enabling OP Stack developers access to the Espresso decentralized shared sequencing network.

Espresso Systems
4 min readSep 8, 2023

Today we are releasing our third testnet of the Espresso Sequencer, Cortado, which includes an integration with the OP Stack. We are glad to support the Optimism ecosystem through offering OP Stack developers a means to not only decentralize transaction sequencing but also share sequencing with other rollups for enhanced interoperability. The Espresso Sequencer is a network that will be shared across many rollups in multiple ecosystems to enhance interoperability by making bridging and atomic transactions more efficient and more secure for users. Underneath the hood, it is a consensus protocol with fast finality, high throughput, and the ability to scale to thousands of nodes.

Any rollup can leverage the Espresso Sequencer for transaction ordering and (optionally) data availability, replacing dependance on centralized sequencers. The Espresso Sequencer is designed to offer rollups a means of achieving more credible neutrality, more secure and efficient interoperability, mitigation of harmful MEV, and long-term economic incentive alignment with L1 validators.

The OP Stack is the standardized, shared, and open source development stack that is maintained by the Optimism Collective. It underpins OP Chains including Base, Zora, PGN, with new OP Chains committing to the vision regularly. These early chains, along with OP Mainnet, are already scaling on-chain activity. In the last month, the four OP Chains combined to use 4.6m gas per second, about 3.7x of the gas used on L1 Ethereum in the same period.

The code we have developed to integrate with the OP Stack is open source and available here and documentation, including architecture, can be found here. You can spin up and experiment with a local version of Cortado testnet and the OP Stack integration by following the instructions here.

Optimism Foundation Mission: Leader Election Proof of Concept

Last June, we undertook work on an Optimism Foundation Mission (RFP) calling for development of a Leader Election Proof of Concept. This work is designed as an open, public contribution to support the Optimism Collective’s progress toward technical decentralization. We at Espresso Systems are glad to have the opportunity to work closely with engineering leaders in the Optimism ecosystem and are proud to be able to contribute to this mission. You can find the code specifically related to this work here, documentation here, and our past updates to the community here.

“The integration of Cortado is an exciting milestone for the OP Stack. Not only does it lay the groundwork for additional sequencing protocols for OP Chains, it also underscores the Espresso team’s commitment to open-source values and community contribution.” said Ben Jones of the Optimism Foundation. “This milestone represents a step towards a standard that benefits developers, projects, and the Optimism Collective on the whole.”

Public Deployment with Caldera

In the coming weeks, we will be continuing our work with Caldera to deploy a publicly hosted testnet, including an OP Stack rollup. On this test rollup, users and developers will be able to deploy test contracts, submit transactions, and interact with applications in a real-time testing environment where all rollup transactions are sequenced by the Espresso Sequencer. Through familiar interfaces like MetaMask, users will be able to submit transactions and experience the rapid pre-confirmations provided by the Espresso Sequencer.

Caldera is a leading rollup-as-a-service company that enables developers to launch customized rollups with one click, leaving it up to the developer to choose what data availability, sequencer, and other layers underpin the system. Caldera supports rollups including Manta, Loot Chain, Syndr, and others.

Matt Katz, CEO of Caldera, said: “We’re incredibly excited to work with Espresso to bring decentralized sequencing to the OP Stack. Rollups today are centrally sequenced—meaning they do not yet fully live up to the decentralization ideals that crypto users will come to expect. We’re looking forward to collaborating further with Espresso, and offering decentralized sequencing to our users.”

Join The Espresso Ecosystem

With this release, we are also glad to welcome rollups and applications including Airchains, Kinto, Opside, Cartesi, Omni, and Vistara to the Espresso ecosystem. We are working with all of these teams to support research and integration of the Espresso Sequencer. There are currently a dozen different rollup teams working on their own bespoke integrations. If you are building a rollup or developing an application on a rollup and think you could benefit from the Espresso Sequencer, please reach out here.

Our work on Cortado follows on from our Doppio (Testnet 2) release in July. Doppio achieved competitive throughput benchmarks that showcased 1000 nodes (with a committee size of 10) achieving 29.41 MB/s which is approximately 100–200k ERC-20 transfers per second. Doppio also enabled users to experience fast pre-confirmations as the Espresso Sequencer sequenced their transactions. For that release, we featured an integration with the Polygon zkEVM stack. Now, with the OP Stack integration, the Espresso Sequencer is taking its first steps toward shared sequencing, with the platform being shared by multiple rollups—and multiple rollup stacks.

Be sure to follow along on Twitter and at our website for further updates on Cortado, including our upcoming public network release.



Espresso Systems

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