Persistent 503 on gemini-3.7-flash with Priority tier (Tier 2 paid) — 0% success over multiple retries

Gemini API
1

Hi team,

I’m hitting sustained 503 UNAVAILABLE errors on the Gemini Developer API in production. Priority tier is enabled, billing is Tier 2 (paid), and RPM/TPM quotas are not being exceeded. The model never accepts the request — failures happen at HTTP level before any streamed response.

Environment

  • API: Gemini Developer API (AI Studio API key, not Vertex)
  • Endpoint: POST https://generativelanguage.googleapis.com/v1beta/models/gemini-3.7-flash:streamGenerateContent?alt=sse
  • Model: gemini-3.7-flash
  • Billing: Tier 2 paid project (billing account linked, paid usage history)
  • Service tier: service_tier: "priority" on GenerateContentConfig
  • SDK: google-genai (Python), streaming via generate_content_stream
  • Caller region: EU / Spain.

Workload

  • ~50k input tokens
  • 12 images (multimodal)
  • JSON output + thinking
  • Single synchronous job per user (not batch, not massive parallel fan-out from our side)

Error

Every attempt returns immediately at HTTP layer with:

{
  "error": {
    "code": 503,
    "message": "This model is currently experiencing high demand. Spikes in demand are usually temporary. Please try again later.",
    "status": "UNAVAILABLE"
  }
}

Wrapped as: google.genai.errors.ServerError: 503 UNAVAILABLE

We never receive response body / stream chunks, so we cannot read x-gemini-service-tier to confirm which tier actually served the request.

Retry policy (already implemented)

Exponential backoff on 503-only:

  • Up to 8 attempts (initial + 7 retries)
  • Delays: 5s → 10s → 20s → 40s → 60s → 60s → 60s
  • Total wait ~4–5 minutes per job before giving up
  1. Is gemini-3.7-flash currently capacity-constrained globally, or region/account-scoped?
  2. Does Priority tier apply to streamGenerateContent on Developer API, or only certain endpoints?
  3. Is there a recommended path for production workloads that need reliability on 3.7 Flash (Vertex Provisioned Throughput, Batch, different model pool)?
  4. Any ETA or status page entry for elevated 503 rates on this model?

Cannot ship reliably on gemini-3.7-flash at current capacity.

image
image1567×547 41 KB

Thank you very much!