Pulling up Legacy Systems

I've been discussing the gardening metaphor for IT with many people over the past couple of weeks, and another interesting parallel between IT and gardening came up: Stump grinding.

When you cut down a tree, the trunk falls and is chopped up for firewood or otherwise removed. But the stump stays. There is a specialized piece of equipment for removing tree stumps called a stump grinder, but that is rarely used in private gardens. Instead, the garden owner just leaves the tree stump. If the tree was strong and healthy, the stump might refuse to die and start sprouting new branches. Otherwise, the stump might rot away over a decade or two. In the meantime, it occupies space that cannot be used for anything else. 

It is the same with legacy systems. The organization initiates a legacy replacement project and starts implementing a new system to take over the functionality from the old one. As the new system begins to become usable, some features of the legacy system might even be disabled. But in most cases, you end up with a legacy stump.

This stump is firmly rooted in the IT infrastructure with dozens or even hundreds of connections to other systems and is very hard to pull up. Since the UI has been replaced, nobody can really see the system anymore. Just like when the tree is gone, the stump is forgotten, the legacy stump lives on, invisibly consuming resources and effort. It might even start sprouting brand-new interconnections when teams implementing new systems discover the existence of this semi-secret resource with access to every piece of data in the organization. 

If you do a legacy replacement, you need to make sure you grind away the stump as well. Otherwise, the new system has just added another layer of complexity to your infrastructure.

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