FastFill

Overview

FastFill is a program designed to improve trade execution speed for retail traders by incentivizing API traders to match with passive orders from Retail Profiles. API traders automatically receive a 75% fee discount when their orders match with retail passive orders, encouraging faster fills for retail users.

How FastFill Works

Fee Discount Details

When your API orders match with passive orders from a Retail Profile:

• 75% fee discount is automatically applied to your trading fees
• The discount is reflected in the fee field of fill responses
• No additional configuration or order parameters are required
• The discount applies to all qualifying fills automatically

Identifying FastFill Fills

Fills that qualify for the FastFill discount are marked with a fastfill flag in the fill response. When querying fills via the List Fills endpoint, check the flags array for the fastfill value.

Example fill response with FastFill flag:

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{
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  "id": "...",
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  "market": "BTC-USD-PERP",
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  "price": "50000",
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  "size": "0.1",
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  "fee": "0.25",
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  "flags": ["fastfill"],
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  ...
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}

The discounted fee amount will be reflected in the fee field of the response.

Orderbook Visibility

The orderbook endpoint includes additional fields to help API traders identify retail liquidity available at the best bid and offer:

• best_ask_interactive: Size available on the best ask from retail traders (UI orders)
• best_bid_interactive: Size available on the best bid from retail traders (UI orders)
• best_ask_api: Size available on the best ask from API orders (excluding retail)
• best_bid_api: Size available on the best bid from API orders (excluding retail)

These fields allow you to see how much retail size is available on top of the book, helping you understand potential FastFill opportunities. Query the Get Orderbook endpoint to access this information.

Execution Priority

UI orders (interactive orders placed through the web interface) have queue priority at each price level. This means:

• UI orders are guaranteed to be filled first before API or RPI orders at the same price level
• The priority ensures retail traders receive the best execution when multiple orders exist at the same price
• API traders matching with retail passive orders benefit from the FastFill discount while respecting this priority system

Benefits

• Faster Execution: Retail orders get filled more quickly as API traders are incentivized to match with them
• Lower Fees: API traders benefit from reduced trading costs when matching with retail liquidity
• Transparent: Orderbook fields clearly show retail liquidity available at the top of the book
• Automatic: No special order types or configurations required - the discount applies automatically