Monaco uses a central limit order book. The best price executes first. At the same price, older resting orders execute before newer orders.Cancel requests are prioritized ahead of new orders. Monaco targets sub-millisecond matching and settles on Sei, whose single-slot finality is designed for confirmations in less than 400 ms.
Market Or Limit?
A limit order is not necessarily a maker order: it may take existing liquidity immediately. See Fees for how maker and taker fills differ.
Market-Order Price Protection
Standard market orders have a mandatory 1,000 bps (10%) protective band around a reference price. The reference is the mark price on margin markets, where a perp market can replace the 1,000 bps with its own band (see Perp price band). Otherwise, it is the median of best bid, best ask, and the recent trade price when the book is two-sided with a spread no wider than 1,000 bps; a missing or wider book uses the recent trade price alone.The recent trade price is the median of the last five liquidity-taking orders, counting each order once at its last fill price. New markets pad missing observations with their oldest one, so it takes three taking orders at a new level for the reference to follow.A client can tighten the band but cannot widen it beyond 10%. Limit orders are not subject to this market-order band.
A protective band limits execution prices. It does not guarantee that the entire order will fill.
How Long An Order Stays Active
GTC does not apply to market orders. The Order Management reference contains payload requirements, supported combinations, and order management behavior.
Previewing An Order
Risk simulations use the same protective band and matching walk as placement. Accepted previews report simulated quantity, average and worst fill prices, slippage, and any remainder. The full reference preserves the response fields and implementation details.Full Orderbook Reference
Full Orderbook Reference
Market Design
Monaco uses an orderbook built for fast, transparent execution:- Central Limit Order Book (CLOB): Monaco uses a central limit order book to facilitate trades.
- Price-time priority: Better prices are executed first. At the same price level, older resting orders execute before newer orders.
- Prioritized cancels: Cancel requests are handled ahead of new order creation, so traders can avoid stale exposure, especially in volatile market moves.
- Low-latency matching: Monaco’s custom matching engine targets sub-millisecond order-matching.
- Fast settlement and finality: Monaco settles on Sei, which provides single-slot finality designed for confirmations in
<400ms.
Order Types
- Market orders: Execute immediately against available liquidity inside a protective price band (see Market-order price protection below). They prioritize execution over price, but the band bounds how far the fill price can move.
- Limit orders: Specify both quantity and a price limit. They can rest in the order book, or fill immediately if they cross available orders.
- Conditional orders: This includes take-profit and stop-loss (TP/SL) orders, which convert to a market order when the mark price meets a condition.
Market-order price protection
Every market order executes inside a mandatory server-side protective price band of 1,000 bps (10%) around a robust reference price — the market’s mark price on margin markets; otherwise the median of best bid, best ask, and the recent trade price when the book is two-sided and not degenerate (its bid-ask spread is at most 1,000 bps); otherwise the recent trade price alone. The recent trade price is the median of the prices set by the market’s last five liquidity-taking orders, not the single last trade, so one or two taking orders that trade far from the market do not move the band; a real move is followed from the third taking order at the new level. Each taking order counts once, at the price of its last fill, so an order that sweeps three price levels contributes one, not three, and the resting orders it fills add nothing. A market with fewer than five taking orders so far counts its oldest one in the empty places, so even a newly listed market needs three taking orders at a new level before the band follows. Fills that would occur beyond the band are cut off:- The portion that fills inside the band settles; any remainder is cancelled, so the order comes back partially filled.
- If no quantity is available inside the band, the order is rejected as insufficient liquidity.
- A market order on a market with no usable reference price (no mark, a degenerate book, and no trade history) is rejected as unavailable.
slippageToleranceBps can only tighten this band; it can never widen it past the market’s band. Limit orders are unaffected — use a limit order to trade beyond the band. The order-risk simulation endpoints run the same walk under the same band and surface the same rejections, so a preflight check matches placement — and because that same simulated match is what admits the order, they also return what it would execute at: expectedMatchResult, the engine’s simulated fill in the same MatchResult shape a placement returns (totalFilled, remainingQuantity — the band-cut / partial-fill indicator — averageFillPrice, executionPriceRange.worstPrice, actualSlippageBps), plus referencePrice for a MARKET preview, priced under your slippageToleranceBps merged with the band. Present only on an accepted preview. See Pre-trade simulation.Time in Force (TIF)
- Fill-or-kill (FOK): The entire order quantity must be executed at a given limit price, or it is cancelled. This is most suitable for large block trades and specific hedging mechanisms.
- Immediate-or-cancel (IOC): This executes any available portion of the order, regardless of market order or limit order, and cancels the rest. This reduces the risk of resting orders in fast-moving markets.
- Good-till-cancelled (GTC): Remains active until executed or manually cancelled, and applies only to limit orders, not market orders. This persists across sessions.