5.41 Quotes From the Future: Clock Drift and the Latency Floor
A quote stamped newer than light can travel isn't fast, your clocks disagree. Fix chrony first, then use an empirical latency floor (half the fastest ping) to catch and correct cross-venue drift.
You are quoting a perp in Frankfurt, blending feeds from Kraken, Deribit, and OKX into one fair value. An OKX quote lands stamped 12 milliseconds ago. OKX's matching engine sits in Singapore. Light through fiber from Singapore to Frankfurt takes roughly 90 milliseconds one way, and the packet still has to reach you, so a 12ms-old quote cannot exist. Either physics broke or your clocks disagree. They disagree. That timestamp predates its own flight, and if you feed it into the cross-exchange fair value from the old article "Cross-Exchange Fair Value for Crypto Perps" you are pricing off a number that lies about when it was true.
This bites the moment you run more than one geo-distributed feed. The old article "Microprice: Better Than Mid Price?" assumed the book you read is the book that exists right now. Across venues separated by continents, "now" is a negotiated quantity, and getting it wrong adds noise to fair value exactly when the feeds disagree most, which is during fast markets.
First, fix your own clock
Before you blame the exchange, look at your own machine. A trading box with a sloppy time service drifts, and a drifting local clock makes every remote timestamp look wrong by the same offset. If you see impossibly fresh timestamps across all venues at once, the common factor is you.