Definition. The widest bid/ask spread, in basis points of mid-price, seen at any single moment within the bucket.

Interpretation. Where the average shows the norm, this captures the worst instant - the briefest, most expensive moment to trade. Spikes flag momentary liquidity gaps from news shocks, flash moves, or pulled orders, making it useful for risk monitoring and execution timing.

Technical. Maximum of (best ask - best bid) / mid_price, in basis points, within the resolution bucket.