Visualforce Transient keyword Performance Tuning

Use the transient keyword to declare instance variables that can’t be saved, and shouldn’t be transmitted as part of the view state for a Visualforce page. For example:

    Transient Integer calculateTotalOpportunityAmount;

Common use case: use transient keyword for field on a Visualforce page that is needed only for the duration of a page request, but should not be part of the page’s view state and would use too many system resources to be recomputed many times during a request. Example below:

    transient public List connections { get; private set; }
    transient public List previousEmployers { get; private set; }
    transient public Set hashTags { get; private set; }

    private List retrievePreviousEmployers() {
        List a = new List();
        a.add(new Account(Name = 'GE'));
        a.add(new Account(Name = 'Siemens'));
        a.add(new Account(Name = 'EADS'));
        return a;
    }

   private List retrieveConnections() {
        return [
            SELECT Id, Name
            FROM Contact
            OFFSET 1
        ];
    }

 private Set retrieveHashTags() {
        Set s = new Set();
        s.add('#where');
        s.add('#dreamforce');
        s.add('#pto');
        s.add('#highlights');
        s.add('#bestpractice');
        s.add('#protip');
        s.add('#iwantapony');
        s.add('#hr');
        return s;
    }