What are you using for monitoring / what generated these logs? Unless your monitor is attempting a connection every, e.g., one second, you're going to end up w

What are you using for monitoring / what generated these logs? Unless your monitor is attempting a connection every, e.g., one second, you're going to end up with the "exact periods" you describe (i.e., presumably your monitor is only attempting to connect once every 30s). Also, this would be more indicative of a problem with your web host, not the .io root name servers, assuming the TTLs on your RRs are set to > 30s.