What it means

PreVOP sent the verification request to the upstream VOP provider but did not receive a response within its configured timeout. Your request did not complete; no verification result is available.

When you'll see it

• The upstream provider is under load and its response latency exceeded PreVOP's deadline.
• A transient network disturbance between PreVOP and the upstream delayed the round-trip.
• The upstream is in a partial-outage state — serving some requests, timing out on others.
• A large request payload is taking longer to process than typical traffic.

Example response

HTTP/1.1 504 Gateway Timeout
Content-Type: application/problem+json
X-Request-ID: 550e8400-e29b-41d4-a716-446655440000

{
  "type":    "https://errors.prod.prevop.alseda.eu/errors/upstream-timeout",
  "code":    "UPSTREAM_TIMEOUT",
  "title":   "Upstream provider did not respond in time",
  "status":  504
}

How to fix

1. Retry the request with a fresh X-Request-ID. Timeouts are usually transient and a retry normally succeeds.
2. Keep retry attempts bounded — one or two retries at increasing intervals (e.g. 1 s, then 5 s) is enough; retrying indefinitely in a tight loop does not help.
3. If your own request budget has a tight deadline, consider a shorter client-side timeout so you fail fast and can route differently.
4. If timeouts persist for more than a minute, treat it as a provider outage and stop hammering — alseda's upstream monitoring will have picked it up.

Related

• Customer API Contract §4.5 — UPSTREAM_TIMEOUT example
• See also: UPSTREAM_UNAVAILABLE — same general class of upstream failure, where the provider actually responded but with an unusable result.