Software module architecture needed

I need help in the design of an object.The object is a list of records.Records can be added, removed or modified by clients (using a Web API or another means).The clients should be notified of any new I need help in the design of an object.The object is a list of records.Records can be added, removed or modified by clients (using a Web API or another means).The clients should be notified of any new update to Refresh their interface (Listeners?)Some concurrency handling is needed.1-If an Item is deleted by client A, and shortl...