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 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.

Limit types

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.

Contact Ably to discuss a limit that needs adjusting to fit your use case or needs at ably.com/support.

Viewing your limits

1. Log in

   Log in to your account.

2. Navigate to limits

   Select Limits from the Account menu.

3. View notifications

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

Exceeding a limit

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.

How limits are enforced

Exceeding the limit depends on the limit type:

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.

Examples: Number of concurrent connections, 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

Notifications

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

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

Application limit	Free	Standard	Pro	Enterprise
Number of apps (per account) the maximum number of applications that can be created per account	100	100	100	100
Number of API keys (per account) the maximum number of API keys that can be created per account	100	100	100	100
Number of rules (per account) the maximum number of channel rules that can be created per account	100	100	100	100
Number of namespaces (per account) the maximum number of namespaces that can be created per account	100	100	100	100

Message limits

Message limits relate to the number, rate and bandwidth of messages consumed across your account. Message count limits and data transfer (bandwidth) limits are enforced separately.

Message limit	Free	Standard	Pro	Enterprise
Message rate (per second) the maximum rate at which messages can be published and received across your account each second	500	2,500	10,000	Unlimited
Messages (per month) the maximum number of messages that can be sent and received across your account each month	6,000,000	Unlimited	Unlimited	Unlimited
Message count (per hour) the total number of messages that can be sent across an account per hour	250,000	5,208,000	20,833,000	Unlimited
Message bandwidth rate (per second, KiB) the maximum rate at which data can be transferred through messages each second	2,384	11,921	47,684	Unlimited
Message bandwidth (hourly, GiB) the maximum amount of data that can be transferred through messages each hour	1.2	24.8	99.3	Unlimited
Message bandwidth (monthly, GiB) the maximum amount of data that can be transferred through messages each month	28.6	1,192	4,768	Unlimited
Max message size (KiB) the maximum size of a single published message	64	64	256	256
Default history TTL (hours) the default time that a message or presence message can be retrieved from history	24	72	72	72
Max history / storage TTL (days) the maximum time that a message or presence message can be retrieved from history	1	30	365	365

Channel limits

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

Why concurrent channel limits exist

Unlike many other realtime platforms, Ably’s architectural design ensures delivery of a high quality of service and continuity for clients across changing network conditions and datacenter conditions (such as scaling events, network disruption or hardware failures).

In order to achieve 99.999% uptime, guaranteed message delivery, and reliable message ordering, Ably’s system design can be considered “stateful”:

• Every channel in the system is maintained by at least two nodes at any point in time
• In most cases many more nodes when clients connect through multiple datacenters
• Ably ensures that a channel is active in each regional datacenter that has attached clients

This active management of each channel by nodes in the system allows Ably to:

• Maintain message ordering for each client publishing messages
• Resume connection state recovery for clients that became disconnected
• Handle channel failure or intentional migration of channels between nodes without any loss of continuity

The channel state that Ably maintains comes at a cost in terms of CPU and primarily RAM within the cluster. Therefore, to provide the realtime platform-as-a-service economically to all customers, Ably charges customers based on the number of peak concurrent channels they use and imposes limits for package types.

The peak channel limit is not the total number of channels created over time, but instead is the total number of channels simultaneously active at any point in time. Channels that are no longer in use (no clients attached and no messages being published) are closed automatically by the Ably platform.

Channel limit details

Channel limit	Free	Standard	Pro	Enterprise
Concurrent channels the maximum number of channels that are active simultaneously at any point	200	10,000	50,000	Unlimited
Default last message on channel TTL (days) the default period that the last message on a channel is stored for, when enabled	1	30	365	365
Channel creation rate (per second) the maximum rate at which channels can be created across an account	42	250	500	Custom
Message publish rate per channel (per second) the maximum rate at which messages can be published for each channel	50	50	50	50
Presence members per channel the maximum number of clients that can be simultaneously present on a channel	200	200	200	200
Presence members per channel with server-side batching enabled the maximum number of clients that can be simultaneously present on a channel when server-side batching is enabled	200	5,000	10,000	20,000
Total object size per channel (MB) the maximum size of a channel object	6.5	6.5	6.5	6.5

Understanding presence limits

Presence limits exist as a precaution against high message consumption. For example, 200 clients subscribed to presence events on a channel and all of them join and leave the presence set within a few minutes would result in:

• 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.

Connection limits

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

Connection limit	Free	Standard	Pro	Enterprise
Concurrent connections the maximum number of realtime clients connected to Ably simultaneously at any point	200	10,000	50,000	Unlimited
New connection rate (per second) the maximum rate at which new realtime connections can be made to Ably across an account	42	250	500	Custom
Inbound message rate (per second) the maximum rate at which messages can be published by a realtime connection	50	50	50	50
Outbound message rate (per second) the maximum rate at which messages can be received by a realtime connection	50	50	50	50
Number of channels per connection the maximum number of channels that each connection can be attached to	200	200	200	200
Connection state TTL the maximum duration that Ably will preserve the state of a dropped connection for	2 mins	2 mins	2 mins	2 mins

Integration limits

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

Integration limit	Free	Standard	Pro	Enterprise
Integration rate (per second) the maximum rate at which integrations can be executed, or streamed	250	250	1,000	Custom
Webhook concurrency the maximum number of unbatched webhook requests that can be in-flight at any one time from a given source	25	25	100	Custom
Webhook batch size the maximum number of webhook events that can be sent per batch	50	100	100	100
Webhook batch concurrency the maximum number of webhook batches that can be processed at the same time	1	1	1	1
Max number of queues (per account) the maximum number of queues that can be created per account	5	10	50	100+
Max queue length the maximum number of messages that can be stored in queues whilst waiting to be consumed	50,000	50,000	50,000	50,000
Queue publish rate (per second) the maximum rate at which messages can be published to a queue	250	250	1,000	Custom
Queue TTL (hours) the maximum time that a message is stored in a queue for, before being transferred to the dead letter queue	24	24	24	24

API limits

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

API request limit	Free	Standard	Pro	Enterprise
HTTP API requests (per hour) the maximum number of HTTP API requests that can be made to Ably per hour, excluding token requests	25,000	521,000	2,083,300	Custom
HTTP API request rate (per second) the maximum rate at which HTTP API requests can be made to Ably	50	362	1,447	Custom
Token requests (per hour) the maximum number of token requests that can be made to Ably per hour	60,000	360,000	720,000	Custom
Token request rate (per second) the maximum rate at which token requests can be made	50	250	500	Custom
Control API: authenticated account requests (per hour) the maximum number of requests that can be made to the Control API, per hour, from authenticated users	4,000	4,000	4,000	4,000
Control API: authenticated access token requests (per hour) the maximum number of requests that can be made to the Control API, per hour, for each access token	2,000	2,000	2,000	2,000
Control API: unauthenticated requests (per hour) the maximum number of requests that can be made to the Control API, per hour, from unauthenticated users	60	60	60	60

Next steps

Pricing

Understand pricing models and choose the right package

Billing

Learn about billing and invoicing

Upgrade package

Upgrade your package for higher limits

Contact support

Discuss custom limits for your use case