I am using ExtJS Grid and its getting pretty slow with 3000+ records. Sorting takes about 4 seconds. Compared to other more Javascript tables, this is pretty slow. I am thinking maybe to use pagination in my table. However after reading the documentation, I am still a bit unsure about how pagination works in extjs. Does this pull data from the server each time u turn a page? I would prefer that wasn't the case. I would prefer the 3000 records are saved in the browser and then what is rendered is just a portion of those rows. Also I am using Extjs version 4.2.1. If I upgrade to version 5. will I get some performance improvements?