Bulkified project triggers

RejectDoubleBooking.apex

trigger RejectDoubleBooking on Session_Speaker__c (before insert, before update) {

    //collect ID's in one list to reduce SOQL
    List<Id> speakerIds = new List<Id>();    
    Map<Id,DateTime> requested_bookings = new Map<Id,DateTime>();
    
    //get all speakers related to the trigger
    for(Session_Speaker__c newItem : trigger.new) {
	    requested_bookings.put(newItem.Session__c,null);
        speakerIds.add(newItem.Speaker__c);
    }
    
    //fill out the start date/time for the related sessions
    List<Session__c> related_sessions = [SELECT ID, Session_Date__c from Session__c WHERE ID IN :requested_bookings.keySet()];
    for(Session__c related_session : related_sessions) {
        requested_bookings.put(related_session.Id,related_session.Session_Date__c);
    }
    
    //get related speaker sessions
    List<Session_Speaker__c> related_speakers = [SELECT ID, Speaker__c, Session__c, Session__r.Session_Date__c from Session_Speaker__c WHERE Speaker__c IN :speakerIds];
    
    //check one list against the others
    for(Session_Speaker__c requested_session_speaker : trigger.new) {
		DateTime booking_time = requested_bookings.get(requested_session_speaker.Session__c);
        for(Session_Speaker__c related_speaker : related_speakers) {
            if(related_speaker.Speaker__c == requested_session_speaker.Speaker__c &&
               related_speaker.Session__r.Session_Date__c == booking_time) {
                   requested_session_speaker.addError('The speaker is already booked at that time');
               }
        }
    }


}

SendConfirmation.apex

trigger SendConfirmationEmail on Session_Speaker__c (after insert) {
	
    //collect ID's in one list of a single SOQL query
    List<Id> sessionSpeakerIds = new List<Id>();    
    for(Session_Speaker__c newItem : trigger.new) {
		sessionSpeakerIds.add(newItem.Id);	
    }
        
    // Retrieve session name and time + speaker name and email address related to ID's
    List<Session_Speaker__c> sessionSpeakers =
            [SELECT Session__r.Name,
                    Session__r.Session_Date__c,
                    Speaker__r.First_Name__c,
                    Speaker__r.Last_Name__c,
                 	Speaker__r.Email__c
             FROM Session_Speaker__c WHERE Id IN :sessionSpeakerIds];
        
    if(sessionSpeakers.size() > 0) {  
            // Send confirmation email if we know the speaker's email address
            Session_Speaker__c sessionSpeaker = sessionSpeakers[0];
            if (sessionSpeaker.Speaker__r.Email__c != null) {
                String address = sessionSpeaker.Speaker__r.Email__c;
                String subject = 'Speaker Confirmation';
                String message = 'Dear ' + sessionSpeaker.Speaker__r.First_Name__c +
                    ',\nYour session "' + sessionSpeaker.Session__r.Name + '" on ' +
                    sessionSpeaker.Session__r.Session_Date__c + ' is confirmed.\n\n' +
                    'Thanks for speaking at the conference!';
                EmailManager.sendMail(address, subject, message);
            }
    }
}