Order types

Velocity has two base order types, market and limit, and three built on top of them: trigger, oracle limit, and scale orders. Flags combine with any of them. Everything here is about perpetual futures; spot order placement is rejected onchain.

Placing and cancelling cost nothing beyond the Solana network fee. The taker fee is charged in USDT, only on the notional that fills. See Trading fees.

Market orders

A market order buys or sells at whatever the market offers now, bounded by a slippage tolerance set on the order. The tolerance is a limit price relative to the current mark price: with SOL-PERP at an illustrative $100.00 and a tolerance of 0.1%, the worst fill price is $100.10, and any fill beyond that does not happen.

The order does not simply hit a resting book. It carries a short Dutch auction whose price walks from a start price in the taker's favor toward the limit, and it can fill against a resting maker order, a maker placing an order specifically to fill it, or Velocity's AMM. See Auctions and How fills work. The price shown at submission is an estimate rather than a promise.

Limit orders

A limit order names the price, and fills at that price or better. Without the post-only flag, a limit order that crosses the market at placement carries its own auction. Once that auction is over the order is resting, and can provide liquidity as well as take it.

With the post-only flag the order can only ever be a maker. It fills at its limit price and earns the 0.25 bps maker rebate rather than paying the taker fee.

Trigger orders

A trigger order sits dormant onchain until a price condition is met, at which point it becomes fillable. A trigger market order becomes a market order when it fires, which is how stop-loss market and take-profit market orders are built. A trigger limit order becomes a limit order, naming the trigger price and the limit price separately, which is how stop-limit and take-profit-limit orders are built.

The trigger price decides when the order wakes up; the limit price decides the worst price it may fill at once awake. A trigger market order has no limit price, so it is bounded by its auction and slippage tolerance like any other market order.

Triggering and filling are two separate steps

The comparison is against a reference price, not the raw oracle. The reference is a median of three price sources, so none of them can fire a stop alone, clamped to a band around the oracle price: 20 bps for contract tiers A and B, 100 bps for tier C, and 250 bps below that. See Contract tiers.

Triggering only makes the order eligible. A keeper still has to submit it, and it then fills like any other order, against a maker or the AMM, never at the reference price itself. Filling is first-come first-served, so a brief touch of the trigger level, network congestion, or a fast reversal can leave an order triggered and unfilled. If the market runs past a trigger limit order's limit before anyone fills it, the order stays open at that limit until price returns or it is cancelled.

A trigger can also fail to fire when the price looks right, because triggering is refused when the market's oracle is not valid, when it has diverged too far from its own five-minute TWAP, when fills are paused, or when the market is in settlement.

And a stop can fire at a level the chart never printed, because the comparison runs against the reference price rather than the last trade. To reconstruct one, switch the chart from "Candles: Fills" to "Candles: Oracle" in its top right corner.

Oracle limit orders

A fixed limit price stops working when the oracle moves: a $99.50 bid with SOL at an illustrative $100.00 is stranded 2.5% below the market once the oracle reaches $102.00. An oracle limit order stores a signed offset instead of a price, and the effective limit is recomputed from the live oracle on every fill attempt.

The stranded bid becomes a buy at an offset of -$0.50, and its effective limit tracks the oracle:

That cuts both ways: on the way down the order follows the oracle to $96.50 rather than filling at $99.50. The effective price is rounded to the market's tick size in the direction of the order; tick sizes are on Market specs.

Scale orders

A scale order places a ladder of limit orders across a price range in one instruction, to build or unwind a position gradually. All of them rest on the book and nothing fills at placement.

• The count runs from 2 to 32 orders.
• The range must run away from the market: a long ladder starts above and buys down, a short ladder starts below and sells up.
• The total base amount must be at least the order step size times the order count.
• Prices are spaced evenly, and the last order sits on the end price.
• Reduce-only, post-only and expiry apply to every order in the ladder.

The 32-rung limit is the same 32 as the total orders a subaccount can hold, so a full ladder only fits an account with no other open orders. See Scale orders in the SDK for the exact parameters.

Order flags

They combine with any type above and with each other where they are not contradictory.

What this means in practice

A trigger market order is the closest thing to a certain fill, at the cost of the slippage; a trigger limit order refuses a bad price, at the cost of being left behind.

For a maker, post-only rules out being charged a taker fee by accident, and an oracle offset holds a quote at a fixed distance from fair value without cancelling and replacing on every tick. The only cost of leaving quotes out is the order slots they occupy, of which a subaccount has 32.