Your secondary DNS only covers silence
On 11 October 2026 a paid DNS provider stopped answering at every location at once for about 54 minutes: its API was storing a setting as an integer where the software expected a string. We look at the other half of the problem, the half no post-mortem covers: what your own network does during those minutes. Microsoft's documentation says the client only switches servers if the previous one is unreachable — an incorrect answer does not trigger failover — that it stays pinned to the alternate for up to 15 minutes, and that on Linux the default cost of a silent resolver is 5 seconds per attempt. With the fifteen-minute check to measure it at home.
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