Avoid Google Calendar API adding an actual event in peoples calendars?

I am using the Google Calendar API with a service account. Idea is that we want to use it purely as an API backend, so we don't have to code it ourselves. That means we do not want it to interfere (or at least make it optional!) with peoples real calendar.

If I make a POST like this:

        var resultingex = service.Calendars.Insert(new Calendar()
        {
            Summary = "Nice new calendar",

        }).Execute();

        var eventIsNice = service.Events.Import(new Event()
        {
            Summary = "I'm a nice event",
            Location = "Copenhagen, Denmark",
            Start = new EventDateTime() { DateTime = DateTime.Now.AddMinutes(15) },
            End = new EventDateTime() { DateTime = DateTime.Now.AddMinutes(45) },
            Attendees = new List<EventAttendee>() { new EventAttendee() { Email = "lars@asano.dk" } },


        }, resultingex.Id).Execute();

It will add to my Google Calendar. That means I cannot use it purely as a backend, as it calls my real calendar.

So my question is: how do I add events that is only existing inside my applications context?

This is how I authenticate with the service:

            var credPath = "client_secret.json";

            var json = File.ReadAllText(credPath);
            var cr = JsonConvert.DeserializeObject<PersonalServiceAccountCred>(json); // "personal" service account credential

            // Create an explicit ServiceAccountCredential credential
            var xCred = new ServiceAccountCredential(new ServiceAccountCredential.Initializer(cr.client_email)
            {
                Scopes = new[] {
                    CalendarService.Scope.Calendar,
                    CalendarService.Scope.CalendarReadonly,
        }
            }.FromPrivateKey(cr.private_key));

            var service = new CalendarService(new BaseClientService.Initializer()
            {
                HttpClientInitializer = xCred,
                ApplicationName = ApplicationName,
            });