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429 Too Many Requests means you exceeded the allowed request rate for your merchant or IP.

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The problem

Burst traffic from tight polling loops, retry storms after 5xx errors, or parallel workers sharing one token can trigger throttling.

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Solution

1

Read Retry-After

If the response includes Retry-After, wait at least that many seconds before retrying.
2

Exponential backoff

Increase delay between retries (e.g. 1s → 2s → 4s) with a maximum cap.
3

Reduce poll frequency

For MoMo, poll every few seconds — not hundreds of ms. Prefer realtime keys.
4

Serialize token refresh

One refresh flow per process; share the cached token across workers.
Last modified on May 22, 2026