MS_MAX_CONCURRENT_REQ VIES error
MS_MAX_CONCURRENT_REQ means the selected member-state VAT registry is receiving too many concurrent requests through VIES.
MS_MAX_CONCURRENT_REQ means the selected member-state VAT registry is receiving too many concurrent requests through VIES.
Country-specific limit
The VIES gateway may be reachable while a single national registry is overloaded or rate-limited.
A German VAT check and a French VAT check can therefore return different availability outcomes at the same moment.
How to handle it
Retry later and consider per-country concurrency limits if you run repeated validations.
Do not convert this response into invalid customer VAT data.
Back off per country, not globally
The limit is the member state's, so throttling your whole queue punishes the 27 countries that were answering fine. Keep one concurrency budget per country code and one retry clock per country code.
Exponential backoff with jitter beats a fixed delay here: a fixed delay makes every one of your workers come back at the same instant and trip the same limit again.
Before you tune anything, check whether that registry is simply unavailable. Rate limiting and an outage produce the same failed batch and need opposite responses — one wants slower retries, the other wants no retries at all until it returns.
Live VIES status by member stateGLOBAL_MAX_CONCURRENT_REQ (the VIES-wide limit)
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