Legacy Systems Age in Reverse

I feel like every job I've ever had in software there has been some old legacy system hanging around that everyone denigrated and perennially spoke about replacing with a newer, shinier system. That replacement was always coming any day now. By the time I'd moved on to a new job, that legacy system was still running, quietly doing some important function for the business, having somehow survived the demise everyone predicted.

The first release of jQuery was in 2006. Within a few years--and every year after--web developers would talk continuously about how outmoded jQuery was, and that no self-respecting developer would still be using it when so many newer, better JavaScript libraries had come along to replace it. Well, guess what. In 2024 (18 years later), jQuery is still in active development, and according to the official jQuery blog, 90% of all websites use jQuery currently. As someone who's been working in the web development space since roughly the dawn of jQuery, I can say that it is still extremely rare that I see a codebase that doesn't use jQuery somewhere, whether as a direct dependency, a transitive dependency, or as part of some 3rd-party tool integrated into the product. jQuery will outlast the human species.

Software systems exhibit the Lindy effect:

The Lindy effect (also known as Lindy's Law) is a theorized phenomenon by which the future life expectancy of some non-perishable things, like a technology or an idea, is proportional to their current age. Thus, the Lindy effect proposes the longer a period something has survived to exist or be used in the present, the longer its remaining life expectancy. Longevity implies a resistance to change, obsolescence, or competition, and greater odds of continued existence into the future. Where the Lindy effect applies, mortality rate decreases with time.

They actually age in reverse. Every year they exist doubles their additional life expectancy. That old system that everyone thinks will be replaced any day now is gaining strength before your eyes, becoming every day less likely to be replaced.

New technologies are the least likely to survive another day, another year. Just as a business that's existed for 100 years is more likely to survive to its 101st year than a 2-year-old business is likely to see its 3rd year.

The implications of the Lindy effect to any of us working in "technology" are so widespread that it's hard to overstate. We're in an industry obsessed with the new, but the new things are constantly passing away as the old geezers are running laps around them. Any new programming language you're excited about right now will be dead long before C is. VS Code will kick the bucket before Vim. Be kind to those elderly technologies around you, because they'll be here long after you're gone.