# Use limitations

EMQX Cloud has fewer usage restrictions than the public cloud IoT Hub platform. The limitations in the table below depend on the number of connections purchased and the hardware performance, and the corresponding parameters have been rigorously tested for performance by EMQ officials.

The performance of the relevant items depends on the deployment specifications, and the specific data is subject to actual usage scenarios.

# Connected Communications

Limitation DescriptionEMQXPublic Cloud IoT Hub
The maximum number of simultaneous online long connectionsDepends on specifications, choice from 1000-10M+. For more than 50K please send tickets for application.10K-500K
Number of connections established per second10K200-500
Number of topics subscribed to by a single clientUnlimited10-100
Single-client subscription requests per secondUnlimited10-10K
Single-client upstream message speedUnlimitedQoS0: 30 messages/second;QoS1: 10 messages/second;QoS2: Not supported
Single-client message downstreamUnlimited50-100 messages/second
Single client throughput bandwidth per secondUnlimited512-1024KB
Single message lengthDefault 1024KB 1-256MB. Adjustable on request.256KB
Maximum offline message storage lengthUnlimited1 week

# Topic Limitation

Limitation DescriptionEMQXPublic Cloud IoT Hub
Topic numberUnlimited50 single product.
PermissionsCustomizeDevices can only subscribe to a limited number of their own Topics for message distribution.
Subscribe/unsubscribe response timeImmediate5-10 seconds