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Build a circuit breaker: closed/open/half-open with a failure window, cooldown, and a single half-open probe

The retry loop's grown-up sibling. Retries protect one call; a breaker protects the whole dependency from a retry storm. The grade is in the half-open state, where letting through one probe instead of all of them is the difference between recovery and re-killing the server.

Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.

The retry loop's grown-up sibling. Retries protect one call; a breaker protects the whole dependency from a retry storm. The grade is in the half-open state, where letting through one probe instead of all of them is the difference between recovery and re-killing the server.

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