Operating Limitations

Operating Limitations

Background

If there are no limitations on connection numbers or data transmission, users may experience reduced MQTT broker performance, such as a slow network connection or operation response, prolonged message latency, message accumulation, or even message discards, and other issues. On the other hand, the protocol limitation also specify the usage limits.

EMQX has therefore specified the following quotas and usage limits for some of the major features.

Reference List

The operating limitations can be classified into:

  • Broker resource limitation: Theoretically, there is no maximum limit. The actual limit varies with the server specification.
  • Hard coding or protocol limitation: EMQX has set these limitations to comply with the protocols or to ensure stable performance. In some projects, EMQX has modified the default setting (as specified in the protocol) to a more reasonable value. You can change the setting with our configuration file.
Description Quota
Client Connection
Maximum concurrent connection devices Unlimited
Maximum device connection rate Unlimited
Maximum MQTT client ID length 65535
Subscription
Maximum subscriptions Unlimited
Maximum subscription rate Unlimited
Per device subscriptions Unlimited
Per device subscription rate Unlimited
Bandwidth
Maximum bandwidth Unlimited
Per device bandwidth Unlimited
MQTT Message
Message Bytes Default 1024KB, Max 256MB
Maximum QoS 2
MQTT Keepalive
Maximun Keepalive 65535 seconds
MQTT Topic
Number of topics Unlimited
Topic level 65535
Topic length Unlimited
Number of topic aliases 65535
MQTT Retained Message
Single Message Size Default 1204KB, Max 256MB
Number of messages Unlimited
Total messages size Unlimited
MQTT 5.0
Number of User Properity 65535
MQTT Add-ons
Number of topic rewrite rules 30
Number of auto subscription rules 30
Number of delayed publish Unlimited
Delayed maximum duration 4294967 seconds
Rules
Number of rules Unlimited
Rule execution timeout Unlimited
Number of single rule outputs Unlimited
Data Bridge
Number of data bridges Unlimited
REST API
Max page size 10000
Number of API Keys 100
Dashboard
Dashboard users Unlimited