# max\_ack\_pending

Aliases:

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`` `max_pending` ``, `` `max_inflight` ``

Hot Reloadable

This is the amount of QoS 1 messages the server can send to a subscription without receiving any `PUBACK` for those messages. The valid range is \[0..65535].

The total of subscriptions' max\_ack\_pending on a given session cannot exceed 65535. Attempting to create a subscription that would bring the total above the limit would result in the server returning `0x80` in the `SUBACK` for this subscription.

Due to how the NATS Server handles the MQTT `#` wildcard, each subscription ending with `#` will use 2 times the `max_ack_pending` value. Note that changes to this option is applied only to new subscriptions.

## Types

| Type      | Description | Choices |
| --------- | ----------- | ------- |
| `integer` | -           | -       |