Promise.all(), Promise.race(), and Promise.any()

What fallback strategy is implemented here?

function delay(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

Promise.race([
  Promise.any([serviceA(), serviceB(), serviceC()]),
  delay(2000).then(() => serviceD())
]);

Simple timeout
Load balancing
Tiered fallback with timeout
This implements tiered fallback strategy: 1) Tries multiple primary services in parallel, 2) Falls back to backup service after timeout, 3) Combines Promise.any() for primary attempts, 4) Uses Promise.race() for timeout control, 5) Provides graceful degradation, 6) Common in high-availability systems.
Error handling chain

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