I'm developing kind of image/profile search application, that is based almost exclusively on AJAX. Main page basically displays profile images and allows user to filter/search and paginate through them.

Pagination works when user scrolls, so the interface has to be very very fast. There will be only 6 (maybe 9, but definitely not more) images displayed on the main page, so users will scroll a lot. I'm currently using very simple JS cache to store results of all the requests in case user decides to go back ... in that case, I simply pull everything out of the cache instead of querying the server.

Client cache

One option that I thought of is to pre-load say 10 pages in front and store them in the cache.

But my biggest issue is filtering/searching, since that completely changes the type of query that goes to the server. My filters aren't very complex, only around 6-7 string/number/enum attributes.

Now if I wanted to do all the filtering in the cache, I would have to duplicate all the search logic and fetch all the data from the server (not just the data I'm displaying), so I could filter the results on client side.

Here raises a question, should I make the cache somehow persistent? Store it into a cookie maybe?

Server cache?

One suggestion might be to use memcached on the server and just store everything there. I'm definiely going to cache away all the results I can, but that doesn't save the server from handling loads and loads of AJAX requests.

I'm developing this application on Rails 3, and even though I love it, I wouldn't say it's the fastest thing in the world. Anothe开发者_开发知识库r option that this gives me is to create separate Rack/Sinatra application to handle only the AJAX requests. By this I mean requests from the main query, not all AJAX.

S3 for images?

Big part of this application are images, even though they're mostly small thumbnails (unless user wants to display it bigger).

At the moment, I don't have problems with bandwidth. My VPS host provides me with 200GB, which should be more than enough (I hope). The problem is loading speed. Would it help if I uploaded all the images to S3 and load them from there, or is this worth doing only for larger files? I'm going to load a lot of 100x150px images, which are generally under 50kB.

Have you looked at SlickGrid. It has an interesting idea of only building the list as users scroll down but then removing the list as the users scroll out of that range.