guide · rate limiting

Rate limits and concurrency, under control.

Cap how many jobs start per second, or how many run at the same time, so a busy queue never overwhelms the API or database behind it.

bunqueue gives you two independent knobs per queue:

• Rate limit: how many jobs may start per second (throughput cap).
• Concurrency limit: how many jobs may be active at once (parallelism cap).

Neither is set by default, so queues run unlimited until you say otherwise.

Set a rate limit

Cap a queue at 100 jobs per second:

bunqueue rate-limit set emails 100   # max 100 jobs/second
bunqueue rate-limit clear emails     # back to unlimited

Or from the SDK (works in both embedded and TCP mode):

Bun

queue.setGlobalRateLimit(100);          // 100 jobs per second
queue.setGlobalRateLimit(100, 60_000);  // 100 jobs per minute
queue.removeGlobalRateLimit();

// Awaitable variants: resolve after the server applied the change
await queue.setGlobalRateLimitAsync(100, 60_000);
await queue.removeGlobalRateLimitAsync();

Node.js / Deno

await queue.setGlobalRateLimit(100);          // 100 jobs per second
await queue.setGlobalRateLimit(100, 60_000);  // 100 jobs per minute
await queue.removeGlobalRateLimit();

Python

queue.set_global_rate_limit(100)         # 100 jobs per second
queue.set_global_rate_limit(100, 60000)  # 100 jobs per minute
queue.remove_global_rate_limit()

PHP

$queue->setRateLimit(100);           // 100 jobs per second
$queue->setRateLimit(100, 60000);    // 100 jobs per minute
$queue->clearRateLimit();

Go

err := queue.SetRateLimit(100)       // 100 jobs per second
err = queue.SetRateLimit(100, bunqueue.RateLimitOptions{DurationMs: 60000}) // per minute
err = queue.ClearRateLimit()

Rust

queue.set_rate_limit(100, None, None)?;          // 100 jobs per second
queue.set_rate_limit(100, Some(60_000), None)?;  // 100 jobs per minute
queue.clear_rate_limit()?;

Elixir

:ok = Bunqueue.Queue.set_rate_limit(queue, 100)                    # per second
:ok = Bunqueue.Queue.set_rate_limit(queue, 100, duration: 60_000)  # per minute
:ok = Bunqueue.Queue.clear_rate_limit(queue)

The limit is a token bucket that refills continuously: max tokens spread over the duration window (default 1 second).

Set a concurrency limit

Cap a queue at 5 jobs running at the same time, across all workers:

bunqueue concurrency set emails 5
bunqueue concurrency clear emails

Bun

queue.setGlobalConcurrency(5);
queue.removeGlobalConcurrency();

Node.js / Deno

await queue.setGlobalConcurrency(5);
await queue.removeGlobalConcurrency();

Python

queue.set_global_concurrency(5)
queue.remove_global_concurrency()

PHP

The PHP SDK does not expose this broker command yet. Configure the same server-side limit with the CLI; it still applies to PHP workers:

bunqueue concurrency set emails 5
bunqueue concurrency clear emails

Go

The Go SDK does not expose this broker command yet. Configure the same server-side limit with the CLI; it still applies to Go workers:

bunqueue concurrency set emails 5
bunqueue concurrency clear emails

Rust

The Rust SDK does not expose this broker command yet. Configure the same server-side limit with the CLI; it still applies to Rust workers:

bunqueue concurrency set emails 5
bunqueue concurrency clear emails

Elixir

:ok = Bunqueue.Queue.set_concurrency(queue, 5)
:ok = Bunqueue.Queue.clear_concurrency(queue)

The PHP, Go, and Rust SDKs do not expose the global concurrency helpers yet. The cap lives server-side per queue, so set it with bunqueue concurrency set or from any other client and it applies to workers in every language.

This is a queue-level cap. Each worker also has its own concurrency option that limits how many jobs that one worker runs in parallel:

Bun

const worker = new Worker('emails', processor, {
  concurrency: 5, // this worker runs at most 5 jobs at once
});

Node.js / Deno

const worker = new Worker('emails', processor, {
  concurrency: 5, // this worker runs at most 5 jobs at once
});

Python

worker = Worker("emails", process, concurrency=5)  # at most 5 jobs at once

PHP

// A PHP Worker is intentionally sequential. Run five worker processes when
// this service should process up to five jobs in parallel.
$worker = new Worker('emails', $processor);
$worker->run();

Go

worker := bunqueue.NewWorker("emails", processor, bunqueue.WorkerOptions{
    Concurrency: 5, // this worker runs at most 5 jobs at once
})

Rust

let worker = Worker::new("emails", processor, WorkerOptions {
    concurrency: 5, // this worker runs at most 5 jobs at once
    ..Default::default()
});

Elixir

worker = Bunqueue.Worker.new("emails", processor, concurrency: 5)

The PHP worker processes jobs sequentially by design and has no concurrency option; run more PHP worker processes to parallelize.

Custom time windows (per worker)

The queue-level limit above already supports any window via the duration argument. If you instead want the cap enforced per single worker, use the limiter option:

Bun

const worker = new Worker('emails', processor, {
  limiter: { max: 100, duration: 60_000 }, // 100 jobs per minute, per worker
});

Node.js / Deno

The TypeScript network SDK has no per-worker limiter. Use a custom queue-wide broker window instead:

await queue.setGlobalRateLimit(100, 60_000); // 100 starts/min across all workers

Python

The Python SDK has no per-worker limiter. Use a custom queue-wide broker window instead:

queue.set_global_rate_limit(100, 60000)  # 100 starts/min across all workers

PHP

The PHP SDK supports a custom window as a queue-wide broker limit:

$queue->setRateLimit(100, 60000); // 100 starts/min across all workers

Go

The Go SDK supports a custom window as a queue-wide broker limit:

err := queue.SetRateLimit(100, bunqueue.RateLimitOptions{DurationMs: 60000})

Rust

The Rust SDK supports a custom window as a queue-wide broker limit:

queue.set_rate_limit(100, Some(60_000), None)?;

Elixir

The Elixir SDK supports a custom window as a queue-wide broker limit:

:ok = Bunqueue.Queue.set_rate_limit(queue, 100, duration: 60_000)

The Bun worker limit is enforced client-side by each worker, so with 3 identical workers the effective rate is 3x.

The budget counts job starts, not completions. Admission is synchronous at the processor dispatch boundary, so concurrency: 20 cannot overshoot a max: 2 window. Batch pulling is capped by the same remaining budget: jobs beyond those two starts stay waiting on the broker instead of being leased and parked inside the worker.

The same gate applies to getNextJob() + processJobManually(). Manual processing waits until a start token is available before invoking the processor. When locks are enabled, getNextJob() exposes the broker lease on job.token, and processJobManually(job) reuses that tracked token if its explicit token argument is omitted.

You can also apply a temporary worker-local pause dynamically:

worker.rateLimit(5_000); // do not start another job for at least five seconds

This override works with or without a configured limiter, including workers using groupKey, and never alters tokens already consumed by previous starts.

The worker limiter option is available in the Bun client. In the network SDKs, use the queue-level rate limit shown in each tab or a client-side limiter of your own in the processor.

Using AI agents?

Agents connected via MCP can set and clear both limits in natural language (“rate limit emails to 50 per second”) through the bunqueue_set_rate_limit, bunqueue_clear_rate_limit, bunqueue_set_concurrency, and bunqueue_clear_concurrency tools.

Reference

Control	Scope	Window	How
Rate limit	Queue (all workers)	Any duration (default 1s)	bunqueue rate-limit set, queue.setGlobalRateLimit(max, duration?)
Concurrency limit	Queue (all workers)	n/a	bunqueue concurrency set, queue.setGlobalConcurrency(n)
Worker concurrency	One worker	n/a	new Worker(..., { concurrency })
Worker limiter	One worker	Rolling duration	new Worker(..., { limiter: { max, duration } })
Temporary worker override	One worker	Explicit TTL	worker.rateLimit(ms)

Gotchas

Older servers ignore the duration

Servers older than 2.8.35 ignore the duration argument and always use a 1-second window. Upgrade the server to get custom windows; the client remains compatible in both directions.

Temporary throttle expires server-side

await queue.rateLimit(ms) throttles the queue to ~1 job/sec and the server clears it after ms on its own, in embedded and TCP mode alike. It throws if ms is not a positive finite number.

For rate limiting that must be shared with code outside the queue (for example, an API budget also consumed by web requests), use an external limiter inside your processor:

Bun

const worker = new Worker('emails', async (job) => {
  await ratelimit.limit('email-send'); // external limiter, e.g. Upstash
  await sendEmail(job.data);
});

Node.js / Deno

const worker = new Worker('emails', async (job) => {
  await ratelimit.limit('email-send'); // external limiter, e.g. Upstash
  await sendEmail(job.data);
});

Python

def process(job):
    ratelimit.limit("email-send")  # your external limiter
    send_email(job.data)

worker = Worker("emails", process)

PHP

$worker = new Worker('emails', function (Bunqueue\Job $job) use ($ratelimit) {
    $ratelimit->limit('email-send'); // your external limiter
    sendEmail($job->data());
});

Go

worker := bunqueue.NewWorker("emails", func(job *bunqueue.Job) (any, error) {
    ratelimit.Limit("email-send") // your external limiter
    return sendEmail(job.Data())
}, bunqueue.WorkerOptions{})

Rust

let worker = Worker::new(
    "emails",
    |job| {
        ratelimit.limit("email-send"); // your external limiter
        send_email(job.data());
        Ok(Value::from(true))
    },
    WorkerOptions::default(),
);

Elixir

worker =
  Bunqueue.Worker.new("emails", fn job ->
    :ok = RateLimit.limit("email-send")  # your external limiter
    send_email(job.data)
    {:ok, %{sent: true}}
  end)

Related Guides

• Queue API - Queue configuration options
• Worker API - Worker concurrency settings
• Environment Variables - Server-side rate limit defaults