Hi all  
I have the following class which is called in Flow action when creating events. I am getting the following error when i try to create event.

We can't save this record because the “Type” process failed. Give your Salesforce admin these details. An Apex error occurred: System.LimitException: Too many query rows: 50001 Error ID: 563784318-263669 (-505665031)ccurred: System.LimitException: Too many query rows: 50001 Error ID: 563784318-263669 (-505665031)


The class


public class UpdateNo_ofInterviewsWithTotalActivities {

    // Do not remove this variable as this is used in the trigger to avoid loop
    public static Boolean isUpdatingNumberOfInterviews = false;

  
    /* @description : This method updates opportunity's Number_of_Interviews__c field based on the
    * opportunity's Event subject
    * @param : events list of Event derived from Process builder
    */
    @InvocableMethod public static void updateOppField(List<Event> events) {
        try {
            Set<Id> oppIdsRelatedToEvents = new Set<Id>();

            for (Event evnt : events) {
                String sub = evnt.Subject;
                if (sub != null && (sub.containsIgnoreCase('Interview') || sub.containsIgnoreCase('intvw') || sub.containsIgnoreCase('screen'))) {
                    System.debug('Event Subject is: ' + sub);
                    if (evnt.WhatId != null || evnt.WhatId != '') {
                        oppIdsRelatedToEvents.add(evnt.WhatId);
                    }
                }
            }
            System.debug('oppIdsRelatedToEvents' + oppIdsRelatedToEvents);

            List<Opportunity> oppsList = [SELECT Id, Name, Number_of_Interviews__c FROM Opportunity WHERE Id In:oppIdsRelatedToEvents];
            System.debug('Opportunities with the Event subjects that contains Interview : ' + oppsList);

            List<Event> eventsList = [SELECT Id, WhatId, Subject FROM Event WHERE WhatId In:oppIdsRelatedToEvents];
            System.debug('Events that are related to Opportunities : ' + eventsList);

            Map<Id, Set<Id>> eventOppsMap = new Map<Id, Set<Id>>();
            if (eventsList != null) {
                for (Event e : eventsList) {
                    if (e != null && e.WhatId != null) {
                        String sub = e.Subject;
                        if (sub != null && sub.containsIgnoreCase('Interview') || sub.containsIgnoreCase('intvw') || sub.containsIgnoreCase('screen')) {
                            if (!eventOppsMap.containsKey(e.WhatId)) {
                                Set<Id> eventsIds = new Set<Id>();
                                eventsIds.add(e.Id);
                                eventOppsMap.put(e.WhatId, eventsIds);
                            } else {
                                Set<Id> eventsIds = eventOppsMap.get(e.WhatId);
                                eventsIds.add(e.Id);
                            }
                        }
                    }
                }
            }
            System.debug('Events with Opps map : ' + eventOppsMap);
            List<Opportunity> oppsTobeUpdated = new List<Opportunity>();
            if (oppsList != null) {
                for (Opportunity opp : oppsList) {
                    Set<Id> oppEventIds = eventOppsMap.get(opp.Id);
                    // Do not remove this variable as this is used in the trigger to avoid loop
                    if (oppEventIds.size() > 0)
                        isUpdatingNumberOfInterviews = true;
                    opp.Number_of_Interviews__c = oppEventIds.size();
                    System.debug('Number of Interviews : ' + opp.Number_of_Interviews__c);
                    oppsTobeUpdated.add(opp);
                }
                try {
                    update oppsTobeUpdated;
                }
                catch(DmlException dmle) {
                    System.debug(dmle);
                    System.debug(dmle.getMessage());
                    DBUtils dbUtil = new DBUtils();
                    dbUtil.handleException('Updating opportunities in process builder', dmle.getMessage(), dmle.getLineNumber());
                }
                System.debug('Opps to be updated in the Update No.of Activities class are : ' + oppsTobeUpdated);
            }
        }
        catch(Exception e) {
            system.debug(e);
            system.debug('Exception occurred when updating the events : ' + e.getMessage());
        }
    }
}


In sandbox it is working. In production we are getting this error. Do I need to use Batch Apex? How to implement batch apex in this?