Server side caching for large websites

What is web application caching?

Server side cache is web based software component that allows saving and reading temporary information that takes a long time to compute.

Such technology is used to improve website speed:

• During first request information is generated and stored to cache files.
• During following requests data is simply loaded from website cache, bypassing computing.

To speed up dynamic website data caching mechanism must be equipped with some kind of destructor that would delete cache data when website has been changed; otherwise it would prevent latest information from being displayed.

Expiring cache

Such mechanism adds expiry date to cache file; cache is recalculated if sever date surpass cache date.

Expiring cache is very useful for web applications that contact 3rd party server to receive data that changes continuously.

Let's say we are building weather plugin that contacts weather server to get forecast for 7 days. It takes somewhere 0.5s to 3s to contact weather station, so if we would have an application that waits for weather data with each request our website would slow down to weather server response time.

By using expiring cache we have to contact weather server only once a day with first request, further requests are retrieved from website cache in less than 0.01s

Persistent cache

Persistent caching provides best performance for internal server computing. Functions that provide server side website update, also delete cache files so they are reloaded only if information is changed.