We've been using EPiServer CMS 6 with EPiServer Commerce for about a year now, and the only performance problem we've run into is calculating discounts. When 20+ Commerce promotions are active, it can easily take the system over a minute to calculate the discounts in a cart containing about 10 items. These promotions are a mix of Entry, Order, and Shipping types.
The issue has been narrowed down to calls being made from CalculateDiscounts ->MarketingContext.Current.EvaluatePromotions(...), but that's where it seems go into the Mediachase.Commerce engine. If I disable that EvaluatePromotions call completely, the page loads nearly instantaneously. ECF, catalog, and marketing caching are all enabled in the config files, and the servers running the code are very fast for everything else.
Any tips or thoughts on speediing this up would be GREATLY appreciated as it's really making our shopping cart an unpleasant experience.
We have the same issue in our solution.
Any tips would be greatly appreciated!