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Retry & Fallback · D5

Build a retry chain with the lowest expected cost.

Tap providers to add them to the chain (tried in order, stop at first success). You pay each attempt; if all fail, the penalty is 63. A cheap, flaky first try with a reliable backup can win.
Practice — no rating pressure. Get as close to the optimum as you can; each play teaches the pattern.
Expected cost
63.0
try nothing → pay the 63 penalty
Providers
About this puzzle

Retry & Fallback — practice the decision, scored against the optimum

What does the Retry & Fallback puzzle teach?

A cheap, flaky first attempt with a reliable fallback can beat one expensive reliable call — in expectation.

Why do interviews ask about this?

Retry / fallback ordering is the reliability interview — sequence attempts to maximize success per expected cost.

How is it scored?

The engine computes the provably-optimal answer for the exact instance you played (dynamic programming, shortest-path, or exhaustive search — never a heuristic) and scores your attempt as a percentage of it. No login needed to see your score.