There's a meeting that happens in every company with legacy software. Someone pulls up a whiteboard, draws two boxes labelled "OLD" and "NEW," and announces: "Let's freeze features for 12 months, rebuild everything from scratch, and switch over on a Friday night."
This is the moment when experienced engineers start quietly updating their LinkedIn profiles.
The Problem with Big Bang Rewrites
The "Big Bang" rewrite is famously dangerous because it ignores three uncomfortable truths:
Scope creep is inevitable — Your old system has 10 years of hidden business rules. That weird edge case where orders over $50,000 need secondary approval but only on Thursdays? Nobody documented it. You will miss it. Your users will not.
Market stagnation kills momentum — You can't ship new features while you're rebuilding what you already have. Your competitors will not pause to wait for you.
Switchover risk is catastrophic — If the new system fails on launch day, your business halts. All of it. At once. On a Friday night, because that's when these things always happen.
A Better Way: The Strangler Fig Pattern
Named after the Australian strangler fig, which grows around a host tree until it eventually replaces it, this pattern involves slowly migrating features from your legacy monolith to modern services.
The tree metaphor is apt: the old system doesn't die suddenly. It gets gradually hollowed out until one day you realise it's not doing anything anymore.
How it works:
- Identify one function — Pick something self-contained, like customer notifications.
- Build a new, modern service — Just that one thing. Small. Testable.
- Route traffic to the new service — The old system still runs, but this piece is handled by the new one.
- Repeat — Move on to the next function. Invoicing. Reporting. User management.
Eventually, the old system is doing nothing, and you can decommission it safely. No switchover night. No prayers.
Why This Works for Australian Businesses
It minimises risk. You're shipping value immediately, not waiting 12 months for a "grand reveal." If one small service fails, you roll back just that part, not the entire operation.
More importantly, you learn as you go. The third migration is always smoother than the first, because by then you've discovered where the dragons live.
At Code Nexas, we specialise in this kind of surgical modernisation. We keep the lights on while we renovate the house. Nobody notices the work is happening until they realise everything runs better.
Is your legacy code slowing you down? Get a modernisation audit and let's map out a safe path forward.