Cardano Leios Adds Transaction Cache and Download Limits

Cardano’s consensus team has updated the Leios prototype with new download controls, transaction caching and safeguards for block production. The changes are active on the Leios devnet, where developers can measure their effect on peer load, memory use and node timing.

Leios is a proposed Cardano consensus upgrade designed to increase throughput by separating parts of transaction processing while preserving the security role of Ouroboros Praos.

New Download Logic Controls Leios Traffic

According to the September 8 Consensus Team update, developers rewrote the logic that determines which Leios data a node downloads and which peer provides it.

Nodes now limit both the time spent on each download decision and the memory reserved for pending requests. The newest Endorser Blocks receive priority, while requests for missing transactions are randomized to prevent simultaneous downloads from exhausting the same peer limits.

These controls allow the devnet to test larger Leios data flows within defined time and memory boundaries.

Transaction Cache Prevents Repeated Downloads

The update also adds a dedicated cache for transactions referenced by recent Endorser Blocks. Before requesting data from the network, a node checks both the cache and its mempool and downloads only the transactions it is missing.

Endorser Blocks reference transactions that nodes must locate and verify. Reusing locally available data reduces duplicate network traffic and the work required to reconstruct the associated transaction set.

This is a node-level change. Wallets and decentralized applications continue to submit ADA transactions through the existing Cardano interfaces.

Leios Protects Synchronization and Block Production

The team also addressed another cause of unwanted disconnections between functioning nodes. A node syncing from an older chain position may be unable to validate newer Leios messages. It now pauses those requests until its chain tip catches up instead of requesting data and rejecting the replies.

Developers also capped how long the mempool may spend reading ledger state from disk. This prevents disk access from holding a producer’s block beyond its assigned slot.

Tracing for block forging and chain selection was expanded, while the Leios dashboard now shows where the prototype node spends its processing time. These observability changes have been integrated into the devnet node.

The changes remain confined to the prototype, so Cardano mainnet and current ADA transaction processing are unchanged. The next devnet tests can focus on whether peer load, disk latency and block-forging timing remain within the new limits.