One area where you as shop owner can influence the performance of Aimeos directly is the number of products that are in your categories. The fewer products you have in your categories, the faster your product lists will be generated because the database has a smaller set of products that has to be sorted.
As a rule of thumb, a few hundred products per category is good from a performance point of view. But if you would like to add thousand and more products to one category you may start noticing that generating the product list takes more time than if you only have a few products per category.
If you have the ability to configure the number of products that are listed per page, than you should keep in mind that the fewer products are shown, the faster the page can be delivered to the visitors of your website. Usually, you have to find a trade-off between only showing a few products per page (which are very clearly arranged but products on the next pages are less likely to be bought) and showing as much products as possible (leading to a confused visitor and maybe to a performance loss). The decision should be made keeping in mind the kind of products you are selling.
A good trade-off only from the performance point of view is a value of 48 or 50 products per page (depending on the list view that is used). You shouldn't use a higher value than 100 products per page except you have very good reasons as the performance decrease might be noticeable in this case.