Cardano’s Leios Upgrade

Cardano (ADA) is set to undergo a transformative upgrade that promises to enhance its scalability and efficiency. Tim Harrison, EVP Community & Ecosystem at Input Output, emphasized the significance of the upcoming Leios upgrade, describing it as a potential game-changer for the Cardano blockchain.

Understanding the Leios Upgrade

Harrison explained that Leios will implement a parallel block process, as opposed to processing one linear block at a time. This method, which involves creation, endorsement, and ranking by Stake Pool Operators (SPOs), aims to dramatically increase throughput while maintaining security and decentralization.

> “Leios will be a game-changing upgrade for Cardano. Instead of one linear block at a time, Leios uses a parallel block process – created, endorsed, and ranked by SPOs – dramatically increasing throughput while preserving security & decentralization.”
> — Tim Harrison (@timbharrison) March 26, 2025

Enhancing Throughput with Ouroboros Leios

The Ouroboros Leios version, currently in research and development, targets improved throughput for the Cardano network. By optimizing resource utilization and enabling quicker transaction processing, it aims to overcome scalability challenges present in existing systems.

Leios will function as a high-throughput overlay atop base protocols to mitigate issues like protocol bursts, which can congest the network, and equivocations, which entail double-signing attacks. The goal is to achieve nearly optimal transaction processing while ensuring security in practical network conditions.

Heart of Cardano: Ouroboros Consensus Protocol

The Ouroboros consensus protocol is central to Cardano, facilitating secure and efficient transaction settlement, as well as sustaining network scalability and robustness. Currently, Cardano operates on the Ouroboros Praos protocol, which has brought notable security and scalability enhancements compared to Ouroboros Classic.

Upon its implementation, Leios is expected to broaden the capabilities introduced by Praos. As demand for new applications and bridges (such as Cardano-Midnight and Cardano-Bitcoin) escalates, the existing throughput of nearly 12 transactions per second (TPS) becomes inadequate compared to rivals like Solana, which achieves approximately 7229 TPS. In the context of Ouroboros Praos, security constraints, including a 5-second block relay within a 20-second slot, limit block size and the execution of scripts, leading to underused network resources.

Key Challenges Addressed by Leios

Leios aims to tackle three interrelated challenges commonly faced by blockchains:
– Transaction diffusion
– Transaction validation and availability
– Transaction ordering