Initially: dequeue D of (timestamp, latency) pairs

new point (t, l):
    while true and not empty(D):
        (t', l') := last(D)
        if l > l'
            pop_last(D)
        else
            break
    append to tail

retrieve point:
    while not empty(D):
        (t, l) := first(D)
        if t < now - 30s:
            pop_first(D)
        else:
            return l