---
title: Rate limits and concurrency
description: The request rate per key and the number of jobs per workspace.
---
Two separate limits apply.

## Request rate, per key

Each key has a request budget per window. Every response tells you where you stand:

```http
ratelimit-limit: ...
ratelimit-remaining: ...
ratelimit-reset: 39
```

Over the budget, the API answers `429 rate_limited` with `retry-after`. Reads (status, result, list) have a larger budget than writes. If you poll many jobs, follow `next_poll_after_seconds` and spread the calls; one poll per job every few seconds stays far inside the limit.

## Jobs in flight, per workspace

A workspace may have a set number of generation jobs **queued or running** at once. Images and videos share the one cap. On open.sume.com it follows the funds you added in the past 28 days:

| Funds added in 28 days | Jobs in flight |
|---|---|
| $0 | 2 |
| $25 or more | 10 |
| $100 or more | 20 |
| $1,000 or more | 40 |

Your first API key starts you at 4; once your funds reach a higher step, that step applies. Above 40, [contact sales](https://open.sume.com/contact-sales). Billing shows your current limit and what unlocks the next step.

The submit response reports where you stand in `generation_limits`:

| Field | Meaning |
|---|---|
| `concurrency_limit` | Jobs that may run at the same time |
| `queued_jobs_limit` | Jobs that may wait behind them |
| `accepted_generation_jobs_limit` | The two together: the cap on jobs in flight |
| `accepted_generation_jobs` | Jobs in flight now |
| `queue_capacity_remaining` | How many more you can submit now |

A submit past the cap is refused, not queued, and is not charged: it gets `400 concurrency_limit_reached` with the cap in the message, for example "Maximum number of concurrent requests (4) has been reached".

Wait for a job to reach a terminal state, then submit the next. A worker pool sized to `concurrency_limit` keeps you under the cap.

## Overload

Under a sudden burst the API may answer `503 database_busy` with `retry-after`. It is short; retry after the delay.

## Higher limits

On open.sume.com the cap rises as you add funds, up to 40. For more, [contact sales](https://open.sume.com/contact-sales) before a planned traffic increase.