@arjunchahal Your code syntax / structure looks correct.
Make sure the database you created also has those fields (and that you published your changes). In the sample code you provided you have a field called title and a field called data. These must also be fields / columns in your Purchase database. So if those fields / columns do not exist, then the information will not get saved anywhere.
Also, make sure that the database Id is in fact ‘Purchases’ and not ‘purchases’ or else the code will assume the database collection does not exist if it finds no matches.
You may want to consider changing the static word variable “Member plan purchased” to a dynamic variable such as: event.order.planId to save the Plan ID to possibly search / query / filter it later. Right now the actual words “Member plan purchased” will be saved into the database.