today I want to give one more explanation of how to use caching and slots for caching purposes. Also there are plenty of articles on the subject,  I want to give one more with simplest recipe. So, if you need to cache something, you'll need to follow this procedure:

1. declare you class as something that inherits IPrefetchable
2. Create some placeholder in your class for storing items in the cache
3. Implement Prefetch
4. Implement GetSlot

Take a look on the code below, how it can be done:

public class ArTranFetcher : IPrefetchable
{
	private List<ARTran> _arTranList = new List<ARTran>();
 
	public void Prefetch()
	{
		_configurableList = new List<ARTran>();
 
		var dbRecords = PXDatabase.Select<ARTran>();
		foreach (var csAttributeDetailConfigurable in dbRecords)
		{
			_arTranList.Add(csAttributeDetailConfigurable);
		}
	}
 
	public static List<ARTran> GetARTrans()
	{
		var def = GetSlot();
		return def._arTranList;
	}
		
	private static ArTranFetcher GetSlot()
	{
		return PXDatabase.GetSlot<ArTranFetcher>("ARtranFetcherSlot", 
			typeof(ARTran));
	}
 
}

few more explanations on presented code.

1. Placeholder will be _arTranList 
2. GetSlot will be monitoring database ARTran ( because of typeof(ARTran) statement ). So each time ARTRan will be updated, GetSlot will be executed automatically via framework.
3. In your code you can get cached valus via following line of code: var arTrans = ArTranFetcher.GetARTrans();

with usage of such tricks, you can optimize plenty of staff. The only warning would be don't cache ARTran, as it will swallow up all memory of your server.