OKX

What I use it for

• The crypto leg of the bot fleet — BTC and the curated cluster of perps the regime-rotator trades. Demo first, live when a strategy survives walk-forward + a 60-trade live audit.
• Spot BTC and stablecoins for the cash-out path: equities → fiat (IBKR) and crypto → stables/BTC (OKX) both feed the same downstream banking leg.
• One account that does spot + perps + simple earn. Routing inside OKX is faster than bouncing between two venues.

Why I picked it

• API quality. REST + WebSocket are documented and consistent. Order responses match what actually happened; the demo endpoint matches the live endpoint. The bots in my fleet that ran into ghost-fill problems weren't OKX's fault — they were ours.
• Demo environment. Not a backtester — a paper account with real order-book reactions. The same tuned-perps strategy code runs unchanged between demo and live.
• Liquidity. Tight spreads on BTC, ETH, SOL and the majors I trade. Not Binance-deep but more than enough for retail size.
• Fee tier ramps quickly. Maker fees go negative at modest volumes; cumulative cost on a bot that turns over its book daily is meaningfully lower than on US-regulated venues.

Honest tradeoffs

• Not available in the US. Hard stop for US residents — if that's you, this isn't your broker.
• Counterparty risk is real. It's a centralized crypto exchange. I size accordingly: no balance I'm not willing to see go to zero overnight. Treasury sits in custody elsewhere; OKX gets working capital.
• Demo ≠ live edge cases. Live still throws fills that demo doesn't — partial fills under stress, occasional API rejections at exchange resets. We've shipped fixes for both; they happen.
• Customer support is exchange-tier. Standard for the category. Not a reason to pick it; not a reason to avoid it.
• Regulatory surface shifts. Crypto venue rules change by jurisdiction every quarter. Check what's allowed where you sit before funding.