What "simulated on the live book" means

Every Burly account, in the challenge and when funded, is a simulated ledger kept by our engine. Your orders are not sent to the Bulk exchange. They are filled against the order book that exists on Bulk at that moment, at Bulk's real fees and real funding. This post explains what that means in practice, because "simulated" covers a wide range of behaviour in this industry and you should know which kind you are trading.

How a market order is filled

The engine keeps a live copy of Bulk's mainnet order book for every enabled market. When your market order arrives, it is matched against the first book snapshot received after the order, never an earlier one, so there is no look-back. The order walks the levels of that snapshot and the fill price is the size-weighted average of the levels it consumed. It does not walk further than 0.5% from the best price; any remainder is cancelled. A large order in a thin book gets the slippage that book implies.

How a limit order is filled

A resting buy fills when Bulk's best ask reaches or crosses your price; a resting sell when the best bid does. The fill price is your limit price, and the quantity filled per snapshot is limited to the size displayed at the crossing levels. The rest stays on the order. A post-only order that would cross on arrival is rejected.

Fees, funding and marks

• Fees are Bulk's published schedule: taker for orders that take liquidity, maker for resting orders that are filled. No markup.
• Funding is applied every hour at the rate Bulk publishes for that market and hour. A position opened less than 5 minutes before a funding timestamp does not collect a positive payment at that timestamp.
• Open positions are marked at Bulk's mark price. Stops trigger on the mark, not on the last trade.

What the simulation does not model

Your order does not rest in Bulk's book, so it has no queue position and no market impact: nobody on the exchange can see it or trade against it. That is why some things are limited. Profit from positions held under 60 seconds may be at most 20% of your total, and trading against stale prices or moving the real book to benefit your account is prohibited. Those rules exist because of what a simulation cannot see, not to catch ordinary scalping.

Every fill can be replayed

Each fill stores the book levels it consumed, the mark and the oracle price. Each breach stores a full snapshot. If you believe a fill or a breach rests on a wrong price, an appeal is decided by replaying the recorded data, not by anyone's recollection.

Where the money is

No money of yours is deposited or traded. Your only cost is the challenge fee. Payouts are real USDC, paid by Burly from its own funds. Burly may trade on Bulk for its own account, including by replicating the positions of funded traders; that never changes your ledger, your limits or your payout.

We put this on the front page and in the footer of every page rather than in a terms document, because a trader should not have to go looking for it.