When legacy modernisation is worth the effort

Every audit we run turns up some version of this. Legacy modernisation is not free, and pretending otherwise leads to bad decisions.

The right architecture for a team of three is the wrong one for a team of thirty, and vice versa. The version that survives contact with a real deadline is the simple one.

When it is worth it

Strangle the old system gradually rather than replacing it at once. There is a version of this that is over-engineered, and it is worth avoiding. It rarely shows up as a line item, which is exactly why it slips.

When it is not

If nothing downstream depends on it and nobody is complaining, it can wait. Small and consistent beats large and occasional here.

How to decide

Every migration needs a way back. The teams that handle this well are rarely the ones with the biggest budgets. Write the reasoning down alongside the decision, because the reasoning is what changes first.

What this looks like day to day

Most systems fail at the seams rather than inside any one component. Three things worth confirming about legacy modernisation before you move on:

• Someone can say what the current setup is without going to look
• Every migration needs a way back — and you know whether that is true here
• There is a way to tell whether the last change to this helped

Worth checking on your own setup before it becomes someone else's problem to fix.