Scale up vs. Scale out. Those require different architectural considerations. E.g. with scale out your chache has to work suddenly in a distributed way. And

Scale up vs. Scale out. Those require different architectural considerations. E.g. with scale out your chache has to work suddenly in a distributed way. And as we all know scale-up is expensive, can quickly become very expensive, and more importantly it has upper limits. In most cases scale-out is actually the only option, even if scale-up would work for some while. Many times I have seen architects go the easy route and scale up. They either get promoted or switch companies until their solution either gets too expensive or can't scale any more. In the meanwhile other systems are interacting with this system and would need to make changes to adjust to a scale-out system. E.g.: A distributed cache can result in lower write performance, or someone else could have overwritten a certain entry because locking failed (e.g. SELECT FOR UPDATE). In many cases those systems join the list of legacy systems.