SPY under the microscope: nanosecond gaps, the spread two ways, quote quality

WITH
    (
        SELECT (formatDateTime(toTimeZone(toStartOfSecond(sip_timestamp), 'America/New_York'), '%H:%i:%S'), count())
        FROM global_markets.cache_stocks_quotes
        WHERE ticker = 'SPY' AND sip_timestamp >= '2026-06-29 13:30:00' AND sip_timestamp < '2026-06-29 20:00:00'
        GROUP BY toStartOfSecond(sip_timestamp)
        ORDER BY count() DESC, toStartOfSecond(sip_timestamp) ASC
        LIMIT 1
    ) AS busiest_sec,
    ordered AS (
        SELECT
            toFloat64(ask_price - bid_price) AS spread,
            bid_price,
            ask_price,
            toFloat64(sip_timestamp - lagInFrame(sip_timestamp) OVER (ORDER BY sip_timestamp, sequence_number)) AS gap_s,
            greatest(toFloat64(least(leadInFrame(sip_timestamp, 1, toDateTime64('2026-06-29 20:00:00', 9)) OVER (ORDER BY sip_timestamp, sequence_number ROWS BETWEEN CURRENT ROW AND 1 FOLLOWING), toDateTime64('2026-06-29 20:00:00', 9)) - sip_timestamp), 0) AS dwell_s,
            rowNumberInAllBlocks() AS rn
        FROM global_markets.cache_stocks_quotes
        WHERE ticker = 'SPY' AND sip_timestamp >= '2026-06-29 13:30:00' AND sip_timestamp < '2026-06-29 20:00:00'
    )
SELECT
    round(count() / 1e6, 2) AS spy_updates_m,
    busiest_sec.1 AS busiest_second_et,
    toUInt8(startsWith(busiest_sec.1, '10:15')) AS busiest_second_in_1015,
    busiest_sec.2 AS busiest_second_updates,
    round(minIf(gap_s, rn > 0 AND gap_s > 0) * 1e9) AS min_gap_between_updates_ns,
    round(quantileExactIf(0.5)(gap_s, rn > 0) * 1e6, 1) AS median_gap_us,
    countIf(rn > 0 AND gap_s = 0) AS identical_timestamp_pairs,
    round(sumIf(spread * dwell_s, bid_price > 0 AND ask_price >= bid_price) / sumIf(dwell_s, bid_price > 0 AND ask_price >= bid_price) * 100, 2) AS time_weighted_avg_spread_cents,
    round(avgIf(spread, bid_price > 0 AND ask_price >= bid_price) * 100, 2) AS per_update_avg_spread_cents,
    round((avgIf(spread, bid_price > 0 AND ask_price >= bid_price) - sumIf(spread * dwell_s, bid_price > 0 AND ask_price >= bid_price) / sumIf(dwell_s, bid_price > 0 AND ask_price >= bid_price)) * 100, 2) AS per_update_premium_cents,
    countIf(bid_price > 0 AND ask_price > 0 AND ask_price < bid_price) AS crossed_updates,
    countIf(bid_price <= 0 OR ask_price <= 0) AS zero_bid_or_ask_updates
FROM ordered