What limitations exist when implementing push notifications?

When implementing push notifications on iOS, the following limitations exist:

• Payload size restrictions. The maximum data size in a push notification is limited (usually 4 KB), which restricts the amount of information transmitted.
• Dependence on network and device state. The device must be connected to the internet, and the user must allow notifications.
• Sending frequency restrictions. Too frequent notifications may lead to blocking or ignoring by the user.
• Background execution. The app can receive notifications but may not always perform long background tasks.
• Certificate and security requirements. To send push notifications, you need to configure APNs with the correct certificates and keys.

Example: if an app sends too many notifications in a row, the user may disable them, which reduces communication effectiveness.