Throttling & Slow mode

Last Edit: Oct 20 2020

Message throttling

Message throttling is a built-in feature that protects the client from message flooding. This can happen if the user is watching many active channels and can cause the UI to freeze, high CPU usage, and degraded user experience.

Chat clients will receive up to 5 messages per second and the API servers will allow small surges of messages to be delivered even if that means exceeding the 5 msg/s rate.

Here is an example of how message throttling works:

In this example, the client will receive several more messages above the 5/s limit (the yellow bar), and once this burst credit is over, the client will stop receiving more than 5 messages per second. The burst credit is set to 10 messages on an 8 seconds rolling window.

Message throttling can be disabled or increased for your application by our support team

Automatic Feature Throttling

When a channel has more than 100 active watchers Stream Chat automatically toggles off some features. This is to avoid performance degradation for end-users. Processing large amount of events can potentially increase CPU and memory usage on mobile and web apps.

  1. Read events and typing indicator events are discarded

  2. Watcher start/stop events are only sent once every 5 seconds

Channel Slow Mode

Slow mode is a channel feature to reduce message noise; when enabled users can’t post more than 1 message per cooldown interval.

The cooldown interval is configurable and can be anything between 1 and 120 seconds. For instance, if you enable slow mode and set the cooldown interval to 30 seconds a user will be able to post at most 1 message every 30 seconds. 

Moderators, admins and server-side API calls are not restricted by the cooldown period and can post messages as usual.

Slow mode is disabled by default and can be enabled/disabled by admins and moderators.

// enable slow mode and set cooldown to 1s
await channel.enableSlowMode(1);

// increase cooldown to 30s
await channel.enableSlowMode(30);

// disable slow mode
await channel.disableSlowMode();

let channel = .messaging, id: "general")

// enable slow mode and set cooldown to 1s
channel.enableSlowMode(cooldown: 1) { print($0) }

// increase cooldown to 30s
channel.enableSlowMode(cooldown: 30) { print($0) }

// disable slow mode
channel.disableSlowMode() { print($0) }

When a user posts a message during the cooldown period, the API returns an error message. You can avoid hitting the APIs and instead show such limitation on the send message UI directly. When slow mode is enabled, channels include a cooldown field containing the current cooldown period in seconds.

const p = channel.sendMessage(msg);

if (channel.cooldown != null && channel.cooldown > 0) {
    p.then(() => {
        // first lock the UI so that the user is aware of the cooldown 
        // restore the UI after the cooldown is finished
        setTimeout(enableSendMessageUI, channel.cooldown * 1000);

await p;

let channel = .messaging, id: "general")

channel.query { result in
  // Channel response includes cooldownDuration field
  let cooldownDuration = result.value!.channel.cooldownDuration
  // Send a message
  channel.send(message: .init(text: "Hello")) { (_) in
      // block the UI you're using
      // StreamChat doesn't have such a function, you need to implement it yourself
      // Set a timer for cooldownDuration interval
      Timer.scheduledTimer(withTimeInterval: cooldownDuration, repeats: false) { (_) in