After a routine certificate rotation, one service pair fails mTLS with unknown authority while everyone else works. Find the break.

The leaf is valid and the root is trusted, yet verification fails. The gap lives in the middle of the chain, and the exact verify code names it before you open a single config file.

Updated Sep 2026 · Grounded in researched DevOps, SRE and platform engineering interview loops, written to a senior-engineer editorial bar, and never padded to hit a word count.

The leaf is valid and the root is trusted, yet verification fails. The gap lives in the middle of the chain, and the exact verify code names it before you open a single config file.

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Next in this trackNightly backups push the database volume to 100 percent utilisation and application latency follows. How do you make the backup behave?Next in this trackOne app instance keeps flapping out of the load balancer pool, yet between bursts it serves traffic happily. Where do you look?Next in this trackRedis latency spikes for a few hundred milliseconds every couple of minutes, right around each background save. What is your hypothesis?

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