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Hedged request

A second copy of a slow call, sent after a short wait, taking whichever answers first. Only for calls that are safe to repeat.

Taught in Chapter 8: Latency Budgets.

More from the same chapter

• Deadline: How long a caller waits for a call before it stops waiting and goes on without it, or fails.
• Fan-out (calls): One request that calls several services at once, and waits for the slowest.
• Graceful degradation: Showing less rather than nothing when part of the system is slow or down.
• Latency budget: A target for the whole request, with a deadline for each call inside it.
• Tail latency: The slowest requests, the p99 and beyond. It grows with every call a page waits on.