Limits

Ably can scale effortlessly as your business grows.

Limits exist in order to minimize the impact on service due to accidental or deliberate abuse of your applications. They also provide a level of protection to your consumption rates if abuse does occur. If you’re on the correct package for your applications and use case, then hitting a limit should be an infrequent occurrence.

Some limits are tied to a package type. For example, the length of time that you can store messages for is dictated by which package you are on, from 1 day on a Free package up to 1 year on an Enterprise package.

Other limits are more technical in nature. For example, the number of channels that a single realtime connection can be attached to, or the rate at which a single connection can publish messages.

Others still are precautions against high message consumption. For example, the number of clients that can be present on a single channel. This is because clients can change state very rapidly and the number of messages generated can be high. An example of this would be 200 clients subscribed to presence events on a channel and all of them join and leave the presence set within a few minutes. This would result in the following messages:

• 200 presence messages published for the enter event.
• 200 × 200 (40,000) messages subscribed to for the enter events.
• 200 presence messages published for the leave event.
• 200 × 200 (40,000) presence messages subscribed to for the leave event.

This highlights the potential for 80,400 messages to be sent in a very short space of time on a single channel. There are options for mitigating this such as utilizing server-side batching. Contact Ably to discuss increasing this limit if you think it’s necessary for your use case.

1. Log in to your account.
2. Select Limits from the Account menu.

To view any limits that you have previously hit, click view recent limits notifications.

If you exceed the limits of your package then it likely means that your app is performing well, and Ably won’t penalize your success by blocking usage for the majority of limits. Normal service will continue to function beyond the limit, up to a point, for certain limits. However, Ably will contact you to let you know that you need to upgrade your package to accommodate your increased usage.

Limits will come into force either because there isn’t any buffer on them, or because you have exceeded the buffer. Exceeding the limit depends on the limit:

Count-based limits

only a set amount of resources can be in use simultaneously. This means that any usage in excess of that limit will be restricted until existing resources are removed, such as the number of concurrent connections, or concurrent channels.

Rate-based limits

the rate at which resources can be used, expressed as their frequency per second. Usage in excess of a rate limit can be rejected locally, such as a publisher trying to publish at a rate in excess of the publish rate per channel. The publisher will have any publish attempts in excess of this rate rejected and have an error code returned. Other rate limits apply rate suppression across your account when exceeded. For example, if the limit for publishing messages into a queue is exceeded by twice the rate, then each message will have a 50% chance of being rejected. The suppression probability is continuously updated based on the publishing rate.

Email notifications are sent out when you are nearing a limit, as well as when you have exceeded it. You will also see these notifications in your account dashboard and can view any limits that you have previously exceeded.

Application limits relate to the quantity of resources that can be created per account.

Message limits relate to the number, rate and bandwidth of messages consumed across you account.

Channel limits relate to the number, rate and membership of channels on your account.

Connection limits relate to the realtime connections made to Ably from your account.

Integration limits relate to the rate and concurrency of webhooks, queues and Firehose.

API request limits are the maximum number of REST API requests, Control API requests and token requests that can be made to Ably.