Compute a backoff delay with full jitter

Double the window on every attempt, cap it, then pick a point inside it.

JavaScript Version 1.0.0 · MIT · by Oveyon · .md

function backoffMs({ attempt, baseMs, capMs, random }) { return Math.round(random * Math.min(capMs, baseMs * 2 ** attempt)); }

Input & expected output

{
  "attempt": 3,
  "baseMs": 500,
  "capMs": 30000,
  "random": 0.5
}

2000

The edge case

{
  "attempt": 20,
  "baseMs": 500,
  "capMs": 30000,
  "random": 0.999
}

29970

Know the limits

• random is an input so the result is testable; pass Math.random() in production. Honor a Retry-After header when the server sends one.
• Every attempt must reuse the same idempotency key: Oveyon deduplicates a saved key for 24 hours, so a late retry does not send twice.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

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