Order Types

Vela supports limit and market orders, each with distinct execution semantics.

A limit order instructs the engine to execute at your specified price or better. If no matching orders exist at that price when the order arrives, the order rests in the book until a counterparty arrives, you cancel the order, or the session ends. Limit orders give you full control over the price you pay or receive, at the cost of uncertain fill timing.

For buy (bid) limit orders, "better" means a lower price — you may be filled at your limit price or below. For sell (ask) limit orders, "better" means a higher price — you may be filled at your limit price or above. In practice, fills usually occur exactly at the limit price.

Limit orders support all four time-in-force options: GTC, IOC, FOK, and Post-Only. See Time in Force for details.

Limit orders are best for market makers who need precise price control, and for traders who want to avoid paying the spread.

A market order instructs the engine to execute immediately at the best available price, walking through the order book as needed to fill the requested quantity. Market orders guarantee execution timing but not execution price.

The engine fills a market order by matching against resting limit orders on the opposing side, starting at the best price and working outward. If there is insufficient liquidity to fill the entire quantity, the order is partially filled and the remainder is cancelled (market orders never rest in the book).

Market orders are best for traders who need immediate execution and are willing to accept the current market price, including the spread and any slippage from walking the book.