Order book

An order book is the meeting place for buyers and sellers. It shows the prices and quantities participants are willing to trade, then matches compatible orders according to public rules.

Every Novrinex market has its own central-limit order book. Bids represent demand to buy, while asks represent offers to sell. The highest bid and lowest ask are the best available prices.

Price comes before time

Orders offering the best price execute first. A higher bid has priority over a lower bid, and a lower ask has priority over a higher ask.

When several orders have the same price, the network sequence decides their order. Earlier liquidity fills before later liquidity at that level.

Suppose the lowest asks are 3 contracts at 100.00, followed by 5 at 100.10. A trader submits a buy order for 6 contracts with a limit of 100.10. The order fills 3 at 100.00 and 3 at 100.10.

The limit is the worst acceptable price. The trader still receives better prices when they are available.

Makers and takers

An order already waiting on the book is the maker because it made liquidity available. The incoming order is the taker because it chooses to trade against that liquidity. Each fill uses the maker’s price.

One order can take liquidity and later make it. A large limit order may trade against several existing prices, then leave its unfilled remainder on the book for another participant.

Maker and taker roles are determined fill by fill. They are used to apply the market’s fee schedule.

What remains on the book

A good-till-cancelled order remains active until it fills or is cancelled. If it fills partly, the remaining quantity keeps its place at the same price.

An immediate-or-cancel order never rests. It takes the available liquidity inside its price bound and then expires. A post-only order does the opposite: it rejects if any part would trade immediately, ensuring that an accepted order adds liquidity.

Risk at placement and execution

Before an order enters the book, Novrinex checks its authorization, precision, market limits, and margin requirement. Collateral is reserved for any quantity that could increase exposure.

A resting order is checked again immediately before a match. Its owner may have withdrawn free collateral, changed another position, or experienced a move in the mark price since placing it. An old approval cannot create a new fill if the account can no longer support the result.

Reduce-only orders receive the same second check. Their combined open quantity cannot close a position and continue into new exposure on the other side.

Order identity

Every accepted order has a permanent ID. The ID remains part of history after the order fills, expires, or is cancelled and cannot be assigned to a new order.

This gives traders and applications an unambiguous way to connect an order with its fills, cancellations, and final state.