Solana's Fair Trade Rule Hits a Snag Amid Concerns Over Leader Discretion

A proposed rule for Solana's ledger aims to enforce fairer trades by prioritizing transactions within batches based on their fee scores. The draft, labeled SIMD-0649, would require non-exempt transactions in each batch to be in non-increasing priority order. This means that higher-priority transactions would appear first in the batch.

The proposal specifies an integer calculation for determining the priority score, which is based on the reward a leader receives for including a transaction divided by its requested cost under the pre-execution cost model. The score includes the priority fee and the unburned portion of the base fee.

However, the proposed rule would not establish one priority queue for an entire slot, nor would it decide which transactions make the block. Leaders would still retain control over inclusion and batch boundaries. The draft aims to prevent a common loophole by requiring each batch except the final one to span at least two forward error correction sets.

The proposal has been met with some criticism, including concerns about latency and potential for leaders to favor their own transactions. A reviewer argued that a leader could still close a batch when it was advantageous to separate conflicting transactions, and asked for present-day batch-size data broken down by scheduler, client, and market conditions.