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FAQs

What is Ouroboros Leios?​

Ouroboros Leios is a next-generation consensus protocol designed to significantly accelerate and scale Cardano. It improves transaction throughput and reduces latency by splitting transaction processing into parallel stages while preserving Cardano’s core security and decentralization. To learn more, visit the Leios development tracker.

What are the key benefits of Leios over other Ouroboros protocols?​

Leios delivers several major improvements:

  • Much higher throughput: up to 1,500+ transactions per second (30–65× current Praos levels)
  • Faster transaction inclusion: parallel processing allows many more transactions to be handled quickly
  • Better user experience: smoother wallets, decentralized finance (DeFi), non-fungible tokens (NFTs), gaming, and high-volume applications
  • Flexible diffusion and voting: nodes can optimize how blocks and votes are shared across the network
  • Strong cryptography: BLS aggregated signatures for efficient committee voting
  • Rigorous validation: ongoing Rust and Haskell simulations plus formal specifications ensure correctness.

What does Leios mean for Cardano users (eg, wallet users, DApp developers)?​

For everyday users, Leios means faster transaction inclusion and a smoother experience across wallets and DApps – especially during busy periods such as airdrops or decentralized exchange (DEX) activity. For developers, it unlocks high-volume applications that were previously constrained by throughput limits. Wallets, explorers, and APIs will require updates to support the new block types, but the transition is designed to be gradual and backward-compatible where possible.

What are the risks or trade-offs of Leios?​

Leios requires modestly higher node resources (recommended: 6+ CPU cores, 100 Mbps+ bandwidth, SSD storage). The added complexity of the block types increases implementation effort, but extensive simulations and formal methods are in place to minimise risks and maintain Cardano’s high security standards.

What are EBs and RBs in Leios?​

Leios uses such block types:

  • EB (endorser block): references and endorses multiple blocks. EBs are produced every ~5 seconds by committee members.
  • RB (ranking block): final ranking and anchoring block produced every ~20 seconds using Praos mechanics for security and finality.

EBs validate and endorse blocks in parallel, and RBs provide the secure, linear final order.

What is the relationship between Ouroboros, Peras, and Leios?​

  • Ouroboros is the overall family of proof-of-stake consensus protocols that powers Cardano
  • Ouroboros Praos is the current live protocol on mainnet
  • Leios is the primary scalability upgrade, significantly increasing throughput through parallel block production
  • Peras is the fast-finality overlay that works together with Leios to deliver both high throughput and ~2-minute high-confidence settlement.

Together, Leios and Peras give Cardano both massive capacity and fast user-facing confirmations while retaining Ouroboros’ proven security.

How does Leios improve performance?​

Leios processes hundreds of blocks in parallel during each 20-second window. The RB is the final security anchor. This parallelism delivers 30–65× the throughput of Praos while maintaining finality. Early endorsement from EBs also gives wallets and apps higher confidence much sooner than the full 20-second window.

How does Leios maintain security with parallel processing?​

Leios keeps Cardano’s strong security model by combining parallel processing (EBs) with a sequential finality layer (RBs). All conflicts and double-spends are resolved at the RB stage. BLS signatures and VRFs ensure only valid blocks from authorised nodes are accepted, maintaining Ouroboros’ provable security guarantees.

What is sortition in Leios, and how does 'Fait Accompli sortition' work?​

Sortition is a probabilistic method for selecting nodes (based on stake) to produce blocks or issue votes. In Leios, it is referred to as 'Fait Accompli sortition' because once a node proves it was selected to produce a block or vote (using a cryptographic proof), no conflicting claims can arise.

What is the block diffusion strategy in Leios?​

Leios supports the freshest-first strategy for propagating blocks and votes. This strategy focuses on the newest blocks or transactions first.

Can the system be sharded or self-regulated?​

Not in its current design. Every node validates the entire chain. Thus, adding more nodes does not inherently increase throughput in the same way sharded protocols do. The community votes on protocol parameters (for example, block size), and the system's load is the same for all. Future research may explore sharding, but it is not yet part of Leios.

How do I estimate node operating costs for Leios?​

Latest simulations show only modest hardware upgrades are needed (6+ cores, 100 Mbps+ bandwidth, SSD storage). Detailed cost estimates are available in the Leios CIP.

How do I keep track of Leios's progress and updates?​

You can follow:

These resources provide transparency and regular updates on ongoing development.

What are the downstream effects of deploying Leios?​

Leios changes how transactions are validated and how blocks and mempools operate. Wallets, explorers, indexers, and APIs will need updates to handle the new block types and higher throughput.

Is Leios production-ready?​

No. Leios is in active development, with prototypes running. Testnet deployment is targeted for 2026, followed by mainnet after thorough testing, audits, and Cardano governance approval. Official updates will be published on this site and the engineering dashboard.