Glossary

Atomic execution

The guarantee that a bundle's transactions land in full and in order, or not at all. A bundle with any failing transaction is dropped entirely.

Auction tick

One 50 ms auction round in the Block Engine. Roughly eight fit into each Solana slot. See Auction Mechanics.

Block Engine

Flowra's central service. It broadcasts the orderflow stream to searchers, validates and simulates bundles, enforces the validator's policy, runs the 50 ms auctions, and forwards winning bundles to the leader. See Architecture.

Bundle

An ordered group of up to 5 signed transactions submitted as one atomic unit into the auction, carrying a tip. See Bundles.

BundleStage

The validator client module that executes winning bundles atomically at the front of the block and runs the tip program crank each leader slot.

Conflict-aware selection

Auction logic that detects overlapping account access between candidate bundles (write-write and read-write conflict; read-read does not) and selects the highest-value combination of non-conflicting bundles within the compute budget.

CU reservation

The share of a block's compute units the validator reserves for auction bundles (configurable, 15% by default), released back to regular flow when no bundles are pending.

Flowra Relayer

A TPU proxy that receives transactions on the validator's behalf, deduplicates them, and forwards them to the Block Engine and the validator, with no added packet delay.

Flowra Validator Client

A validator client built on the Jito-Solana codebase (Agave lineage), extended with Flowra's bundle pipeline, CU reservation flags, and PBP policy push.

Gulf Stream

Solana's mempool-less transaction forwarding design: transactions are pushed directly to upcoming leaders instead of gossiped publicly. The structural reason Solana's orderflow is dark by default.

Leader / leader slot

The validator currently assigned to produce blocks, and its ~400 ms production window.

MEV (Maximal Extractable Value)

Value extractable by controlling transaction inclusion and ordering: arbitrage, liquidations, and (in harmful forms) front-running and sandwiching.

OOA (Open Orderflow Auction)

Flowra's market mechanism: a transparent, permissionless auction over pending-transaction flow. See Open Orderflow & Accountability.

Orderflow

The stream of pending user transactions (swaps, liquidations, transfers) before finalization. See Orderflow on Solana.

PBP (Programmable Block Policy)

Flowra's core feature: validator-defined block composition rules (address screening, program filters, MEV posture, priority pinning, compute quotas) owned by the validator as a policy file, pushed to the Block Engine, and enforced before the auction. See PBP.

PFOF (Payment for Order Flow)

Monetizing orderflow by routing it to paying market makers through exclusive channels; the model Flowra's open market replaces.

Priority fee

The fee users attach to compete for inclusion. On Solana today, effectively a blind auction and a key source of systematic overpayment.

Protocol fee

Flowra's 5% fee on auction tips; the remainder flows to validators and stakers.

Sandwich attack

Harmful MEV where an attacker brackets a victim's trade with its own transactions to profit from induced price movement. Flowra's policy engine detects the wrapping pattern and lets validators reject it.

Searcher

A participant running strategies over the orderflow stream and bidding tip-bearing bundles into the auction. See Searchers.

SFDP (Solana Foundation Delegation Program)

The Foundation's stake delegation program; its rules influence which infrastructure validators can run without losing delegation.

Slot

Solana's ~400 ms block production interval.

State auction

The contest among bundles whose account footprints overlap. Each 50 ms tick resolves state auctions and assembles the winning batch from their winners.

Tip

The searcher's auction bid, paid as lamport transfers to designated tip accounts inside the bundle and measured during simulation. Split 5% protocol / 95% validator and stakers.

Tip account

One of the addresses returned by GetTipAccounts. Transfers to these accounts inside a bundle constitute the bundle's bid, claimed through the on-chain tip distribution mechanism.