I have two child magento websites and one master website, Now I would like to synchronize child sites when something happens to master, For example: When a product is added or a price change - sync to other two child websites. (i.e.) All/Custom admin activities are synchronized between Master and child magento websites.
Note: These Magento stores are not configured like Multi-stores and these are installed separately on different domains.
As you are not using Multi-stores functionally that it become too different to track each of event of one store and then transfer to master website.
Suppose,You will try to like soap api,rest api, Event/observer and other customization.
Then it would create hug perform issue between two website as every time,data will synchronize between site.
In my point view,it is not possible to track each website event for each times.
So you cannot do a complete synchronize child sites with master.
My suggest to use multi store
This is possible, you need your master to have a catalog json/xml output then compare the update time (foreach) product (on master) with the data from the child sites and only save/update child site data if update time is different.
What you need - PHP code to read each item in json/xml - If ID matches, compare update time - If master update time newer, update child product - CRON job pointing to PHP file
If done this in the past with an external json API to update my magento collection data
