Does length of variable name matter with Interpreted languages?

TL;DR Not usually...At least not in some of the ways you might think.

This is a rather interesting question that seems to come up a lot, and I remember reading a ton about this when I first started out, though I couldn't link to any good reads. Essentially it depends on the language and how it was implemented, but even in some of the more intensive implementations, the difference in performance between a=0 and a variable name ridiculously long is minuscule.

Interpreted languages tend to parse the variable names and assign IDs and such, so usually all variable names tend to wind up with names of the same lengths internally anyway. Could an insanely long variable name affect this? Sure. A lot of languages actually have an internal maximum length setup for variable names anyway though, so chances are it would never get to a point where it affected the parsing or application load enough to be an issue, most of the time anyway.

There are a few other performance concerns that may arise depending on database access, data transfer, and so on. Since some of these processes might actually involve the storage or transfer of these huge variable names, it would indeed slow down the process, increase the amount of data transferred and various other issues (most of which could be avoided with proper "good practice" techniques anyway, but that's another story).

Another "performance" concern is code readability and reusability. Want to share your code? Ever work with anyone else? Tried to bring someone new into your little group? Needed help debugging an issue you were having? These problems are compounded exponentially with every goodIntentionedButSlightlyConfusingOverlyComplexVariableNameThatMayOrMayNotActuallyTellYouWhatIAM = "Um, yes? That's me...I think?" Sometimes, less is more.

The general rule of thumb is to make your variable names as short as possible whilst maintaining maximum clarity. It's a balancing act between clarity and length that, all too often, juvenile programmers will tip in the wrong direction. There are also other "best practices" like naming bool variables in a way that asks the question you're expecting a True/False (Yes/No) answer to, or naming functions/methods for the things they do or return rather than something else. These things become common convention because they work. They make our lives easier and the lives of all we expose to the spaghettified mess that is our code. I think in this aspect, the question isn't "do variable name lengths matter?" It's "do I really need that extra long variable name?"