One of the most important keys to website performance is caching. That’s why freistilbox includes multiple caching services, first and foremost the Varnish HTTP cache. On our load balancers, Varnish stores all the content your web application allows to be cached. During the lifetime of the respective cache content, Varnish answers incoming requests right from its memory cache instead of forwarding them to the application boxes. This speeds up delivery by orders of magnitude.

But what about these requests that can’t be cached? Of course, not everything can be delivered from the cache all the time. Before it can be cached, content needs to be generated by your web application at least once in a while. So a certain percentage of web requests must be processed by your application. Each request your application receives is assigned to a single Processing Unit (PU). This PU then executes your application code in order to process and respond to the request.

The number of simultaneous requests that can be handled is limited by the total PU available to your freistilbox cluster which in turn depends on the size and number of boxes that make up your cluster. Up until now, these were the effective PU limits for our freistilbox sizes:*freistilbox S: 5 PU

• freistilbox M: 15 PU
• freistilbox L: 35 PU
• freistilbox XL: 75 PU

After a number of small freistilbox setups experienced occasional overload, we realised that with 5 PU, a single freistilbox S just doesn’t have enough capacity for production websites (except the most static ones). Since modern web browsers open multiple connections to fetch different assets in parallel, even only a single visitor could use up all five available Processing Units and block the website for everyone else. That’s why we recently started to advise customers not to use a single freistilbox S for production websites.

That didn’t feel right, though. There shouldn’t be even a single freistilbox configuration that isn’t up to the task. So we decided to increase the PU limits on freistilbox S, M and L. The new specs are as follows:

• freistilbox S: 10 PU (+5)
• freistilbox M: 25 PU (+10)
• freistilbox L: 40 PU (+5)

With 10 PU, a single freistilbox S still won’t be powerful enough to run a busy community website but it should now have enough capacity to reliably serve a medium website that has a decent cache hit ratio.

Oh, and all existing freistilbox customers have already been auto-upgraded!

freistilbox with more power — for the same price. What’s not to love?

What do you think? Leave us a comment below!