90021: Account-wide channel creation rate exceeded

Requests were rejected because the rate at which new channels were being created across the account exceeded the permitted limit. The limit counts channels newly activated within a period, not those already active.

What you should do

Usually nothing: this is non-fatal, and the SDK retries the channel automatically until it succeeds. If you create channels through the REST API and it matters, retry after a short delay, increasing the delay if it is rejected again. This limit applies to your account's total rate of activating new channels, so spreading them across more connections does not help: every newly activated channel in the account counts towards it. If your account consistently needs to create channels faster, you can request a higher limit.

Why it happens

Your account has a maximum rate at which new channels can be activated across all of its apps, set by your account's limits. When channels are activated faster than that, further activations are rejected until the rate falls back within the limit. Because this applies across the whole account, a channel activation can be rejected even when no single connection is creating channels quickly on its own.

What you'll see

The error is reported with code 90021 and HTTP status 429, with a message of the form Maximum account-wide instantaneous channels rate exceeded; permitted rate = ...; metric = channels.maxRate. Because it is non-fatal, the SDK retries automatically.