Rate limits and sending quotas

Apollo Signal applies named HTTP buckets to high-volume public endpoint groups. Limits are evaluated per API key for normal developer requests.

Endpoint group	Limit	Window
`POST /v1/emails`	300 requests	60 seconds
`POST /v1/emails/batch`	30 requests	60 seconds
Contact endpoints	200 requests	60 seconds
Contact property endpoints	60 requests	60 seconds
Project list, get, and update	60 requests	60 seconds
Segment endpoints	60 requests	60 seconds
Sending domain endpoints	30 requests	300 seconds
Suppression endpoints	120 requests	60 seconds
Topic endpoints	120 requests	60 seconds
Webhook endpoints	60 requests	60 seconds
Metrics and deliverability advisor endpoints	120 requests	60 seconds

Each generated endpoint page repeats its applicable bucket under Requirements. An endpoint without a displayed named bucket is still subject to its documented domain rules, sending quota, and protective platform controls.

Rate-limit response

When a named HTTP bucket is exhausted, Apollo Signal returns 429 as an application/problem+json document and includes:

Retry-After: 12

Retry-After is a whole number of seconds. Wait at least that long, then retry with jitter so concurrent workers do not all resume at once.

const retryAfter = Number(response.headers.get("retry-after") ?? "1");
const jitter = Math.floor(Math.random() * 250);
await new Promise((resolve) => setTimeout(resolve, retryAfter * 1000 + jitter));

Do not assume X-RateLimit-Remaining or reset headers are present.

Sending quotas

Email delivery also has plan-backed quotas independent of the HTTP request bucket:

A project has a per-second send allowance.
An organization has a daily send allowance.
A batch or audience fan-out consumes quota per resulting message, not merely per HTTP request.
Scheduled and test-mode behavior follows the send endpoint’s response and plan rules.

A request can therefore pass the endpoint bucket and still receive a send-related 429. Inspect the problem code, honor Retry-After, and do not bypass the quota by rotating API keys.

Overview

Emails

Metrics

Projects and email logs

Sending domains

Contacts

Contact properties

Segments

Topics

Suppressions

Webhooks

API key usage

Rate limits and sending quotas

Rate-limit response

Sending quotas

​Rate-limit response

​Sending quotas

Rate-limit response

Sending quotas