Order book

Hyperliquid L1 state includes an order book for each asset. The order book works in essentially the same way as all centralized exchanges. Orders are added where price is an integer multiple of the tick size, and size is an integer multiple of lot size. The orders are matched in price-time priority.

Operations on the order book take a reference to the clearinghouse, as all positions and margin checks are handled there. Margin checks happen on the opening of a new order, and again for the resting side at the matching of each order. This ensures that the margining system is consistent despite oracle price fluctuations after the resting order is placed.