# Perpetual Trading

## Order Matching Mechanism

Astros employs a **Price-Time Priority** system, utilizing a **First-In-First-Out (FIFO)** methodology for matching orders.

#### Matching Criteria:

Orders are matched when either of the following conditions is met:

* A **buy (bid)** order price is **equal to or higher** than the best available **sell (ask)** order price.
* A **sell (ask)** order price is **equal to or lower** than the best available **buy (bid)** order price.
* A **market order** is submitted, and opposing limit orders already exist in the order book.

In all cases, orders with earlier timestamps receive priority at the same price level.