A request goes through services A → B → C → D. A, B and C each make up to 3 attempts when their call fails. If D is down, how many calls can one user request send to D?

Options

• ✗ 3
• ✗ 9
• ✓ 27 Correct
• ✗ 81

Why

Attempts multiply at each layer: 3 × 3 × 3 = 27. Retrying at every layer turns an overloaded service into a crushed one. Retry at one layer only, and cap retries with a budget (e.g. at most 10% extra traffic).

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