Notifications are always delayed 0-60 seconds due to the job executing once every minute. On top of that notification delivery might be delayed due to battery saving strategies on the target device. This is purely up to the browser/operating system of the device receiving the notifications and can not be controlled by Softadmin®. This may depend on battery optimization settings, memory usage, if the screen is locked or not, when the app was last opened, when the browser was last opened for other purposes, browser version, operating system version and much more on the target device. This delay may change at any time and may change with updates of the browser/operating system.
The browser used is the browser that the PWA was installed from.
Generally there is no notification delivery delay if the PWA is in the foreground, but the delay may vary widely from no delay to a several hours depending on the above mentioned circumstances. The operating system may choose to stop delivering notifications if the PWA have not been opened for a very long time (usually after several weeks/months).
For example these are some delays observed on a device: