BTC Up/Down Arbitrage: Speed on Short-Window Crypto Markets

Polymarket runs recurring BTC Up/Down markets — will Bitcoin be higher or lower at the end of a 5-minute, 15-minute, or 1-hour window? Predict.fun runs similar 5- and 15-minute crypto rounds on BNB Chain. These markets open and close constantly, and because they track a fast-moving underlying (spot BTC), they reprice every few seconds. That churn creates short-lived pricing inefficiencies, and capturing them is a pure latency play.

Where the edge comes from

A BTC Up/Down contract should track the live probability that BTC closes the window higher. But the contract price and the implied probability from spot don't update in lockstep:

• Spot BTC moves on Binance, Coinbase, and Kraken instantly.
• The prediction-market contract reprices when traders react — with a lag.

In that lag, the contract is briefly mispriced relative to where the underlying already is. A bot that's watching spot and the contract simultaneously can take the correct side before the market catches up, then exit (or hold to the window close) on the corrected price.

The windows are short, so the holding period is short, so capital recycles fast. It's a high-frequency version of the same "price should reflect reality" edge that drives all arbitrage.

Why milliseconds matter

This is the strategy where latency is most obviously the entire game. The inefficiency exists for a window measured in hundreds of milliseconds to a few seconds. If your bot:

• polls an API every 2 seconds, or
• runs an interpreted loop that takes 500ms to decide and place an order,

…the opportunity is gone before you act, and you're taking the other side of someone faster. A competitive BTC arbitrage bot operates on a different timescale entirely — tens of milliseconds from signal to order on the book, using Fill-and-Kill (FAK) orders so you either get the price you wanted or nothing at all.

On a 5-minute BTC window, the difference between tens of milliseconds and 500ms is the difference between the edge and being someone else's edge.

What a real implementation needs

• A fast, faithful price feed. You're trading against where BTC actually is. The feed has to be real-time and aggregated across major venues, since that's what the market ultimately resolves against.
• FAK execution. You don't want a resting order sitting into a window close. Fill-and-Kill takes the price if it's there and cancels if it isn't — no stale exposure.
• Native-speed code. This is why serious short-window bots are written in Rust on an async runtime: no GC pauses, predictable latency under load. An extra 100ms of jitter is the whole margin.
• The risk layer, still on. Even a fast strategy needs a circuit breaker and a trade-size floor — speed without guardrails just loses money faster.

Getting started

The open-source Prediction Market Toolkits includes a BTC bot that values Predict.fun's live Up/Down rounds against a spot price and buys when the edge clears fees, one entry per round, on a Rust core with the shared risk layer. It runs in dry run, no live order has been tested through it yet, and it refuses to go live on any price but Binance's, which those rounds settle on. Whatever you run, use dry-run first to see how many windows your config actually catches a fillable edge on before you commit capital.

A related cross-venue play is Kalshi ↔ Polymarket arbitrage — locking the spread between two venues instead of racing a single one.

Disclaimer

Trading prediction markets involves real financial risk. Short-window arbitrage is latency-sensitive and unforgiving of slippage, and nothing here is financial advice. Software is provided as-is without warranty. Always test in dry-run before deploying real capital, and comply with each venue's terms of service and your local regulations.