Is it crazy to not rely on a caching system like memcached nowadays ( for dynamic sites )?

Question

I was just reviewing one of my client's applications which uses some old outdated php framework that doesn't rely on caching at all and is pretty much completely database dependent.

I figure I'll just rewrite it from scratch because it's really outdated and in this rewrite I want to implement a caching system. It'd be nice if I could get a few pointers if anyone has done this prior.

• Rewrite will be done in either PHP or Python
• Would be nice if I could profile before and after this implementation
• I have my own server so I'm not restricted by shared hosting

Answer 1

Since Python is one of your choices, I would go with Django. Built-in caching mechanism, and I've been using this debug_toolbar to help me while developing/profiling.

By the way, memcached does not work the way you've described. It maps unique keys to values in memory, it has nothing to do with .csh files or database queries. What you store in a value is what's going to be cached.

Oh, and caching is only worth if there are (or will be) performance problems. There's nothing wrong with "not relying" with caches if you don't need it. Premature optimization is 99% evil!

Answer 2

If your site performance is fine then there's no reason to add caching. Lots of sites can get by without any cache at all, or by moving to a file-system based cache. It's only the super high traffic sites that need memcached.

What's "crazy" is code architecture (or a lack of architecture) that makes adding caching in latter difficult.

Answer 3

Caching, when it works right (==high hit rate), is one of the few general-purpose techniques that can really help with latency -- the harder part of problems generically describes as "performance". You can enhance QPS (queries per second) measures of performance just by throwing more hardware at the problem -- but latency doesn't work that way (i.e., it doesn't take just one month to make a babies if you set nine mothers to work on it;-).

However, the main resource used by caching is typically memory (RAM or disk as it may be). As you mention in a comment that the only performance problem you observe is memory usage, caching wouldn't help: it would just earmark some portion of memory to use for caching purposes, leaving even less available as a "general fund". As a resident of California I'm witnessing first-hand what happens when too many resources are earmarked, and I couldn't recommend such a course of action with a clear conscience!-)

Answer 4

Depending on the specific nature of the codebase and traffic patterns, you might not even need to re-write the whole site. Horribly inefficient code is not such a big deal if it can be bypassed via cache for 99.9% of page requests.

When choosing PHP or Python, make sure you figure out where you're going to host the site (or if you even get to make that call). Many of my clients are already set up on a webserver and Python is not an option. You should also make sure any databases/external programs you want to interface with are well-supported in PHP or Python.