Espresso is not building composability for rollups. It is building composability for all the sovereign systems in the world, whether they are onchain yet or not. The world runs on a network of sovereign systems. Governments, companies, and individuals each have their own authority and identity. These systems are complex: governments contain people and companies, yet companies can operate across multiple governments. The trust relationships between these systems are often ambiguous and carry uncompensated risk. Yet the global economy demands that we communicate and transact across these sovereign boundaries as efficiently as possible. Therefore, we need a fast, efficient mechanism for cross-boundary coordination that operates under minimal trust assumptions (which reduces risk and ambiguity) without compromising the sovereignty of each participant. A system that forces participants to compromise their independence (via a single execution environment, sequencing protocol, etc.) will capture few participants. Without trust-minimized, onchain protocols, we've been historically forced to accept risk in favor of speed. There are two components to cross-system communication: input data and proofs over said data. Both must be fast and trust-minimized for the overall mechanism to be credible. A mismatch in trust assumptions between a proof and its data undermines the whole mechanism. Data finalized by an economically secure consensus protocol is undermined if verified by a single-signature proof system. Conversely, a ZK+TEE multi-proof is undermined if its input data comes from a single trusted party. (The trust spectrum of proof systems warrants its own post; we'll just focus on fast finality here.) Trustlessness and speed exist on two independent axes. We often assume the relationship between them is linear--that for one unit of trust you give up one unit of speed. This is wrong. Careful protocol design can achieve strong trust guarantees at low latency. A high-level relationship between trustlessness and speed is shown below. Espresso's goal is to operate at the most efficient point on this curve so it can serve as the credible base layer for the broadest spectrum of sovereign systems. It achieves this via a decentralized PoS validator set providing censorship resistance and economic security, coupled with HotShot, a low-latency, high throughout consensus protocol purpose built for this role. (More posts about exciting updates to HotShot coming soon!)