Legacy is not just dusty old code and outdated systems. Legacy is the drag you didn’t see coming when it hits you mid-deploy. A three-minute tweak takes twenty. One client-ready fix breaks three other things.

Legacy and technical debt aren’t the same. Legacy code is old code, sometimes good, sometimes bad. Good legacy is readable, well-structured, documented. You can still onboard new developers into it without much pain. Bad legacy is a black box: messy, undocumented, and fragile.

Technical debt, on the other hand, isn’t about age. It’s about trade-offs. You borrow time today by cutting corners, and you repay later with interest. Debt is a choice; legacy is a condition. And the way you handle them is different.

Founders don't like to talk about legacy. Investors often don’t know how to spot it. But it’s there, silently eroding speed, burning cash and blowing timelines, and making the business harder to scale. Let’s shine a light on bad legacy.

Legacy isn’t always bad

Some code grows old gracefully. If dependencies are up to date and deployments are fast, you don’t need to lose sleep over a ten-year-old module. In fact, stability is a blessing.

Here’s a useful sanity check: if the feedback cycle is short, things are probably fine. Quick deploys, fast rollbacks, and minimal production regressions are the best indicator that teams are keeping their house in order.

The real problem is harmful legacy. These are the parts of the system you touch all the time but can’t trust. That’s where the whole engineering team slows down without realising why. It’s when your engineering team is starting to complain more and motivation is draining.

When feedback loops get long and fragile, legacy isn’t technical anymore. It’s cultural. That’s when you should worry.

Our approach on legacy & tech debt

What can investors do about legacy?

Spotting legacy is one thing. Protecting your investment from it is another.

The most valuable move? Make sure technical work is visible on the roadmap. Don’t just ask about product roadmaps, but ask about the boring stuff too:

  • What percentage of the roadmap is technical rather than shiny?
  • What percentage of time goes to maintenance?
  • What big refactors are needed to stay scalable?

As an investor, you should demand that time and budget are consistently allocated to staying technically relevant. Sometimes that means big initiatives make it onto the roadmap. Other times it’s simply an agreement that 10–15% of engineering time goes to maintenance and upgrades. Both are fine, as long as they exist.

Think of it as insurance for your capital. You wouldn’t buy a building without a maintenance plan. Don’t back a product without one either.

The easiest way to get resistent leadership on board is by quantifying the pain. Show how much time bugs waste in a metric they care about: $$$. Show how much revenue slipped because the team couldn’t deliver fast enough. CFOs don’t argue with numbers.

How we spot legacy during audits

During technical due diligence, the fastest way to smell legacy isn’t to read code line by line. It’s to look for signals that tell you the system has become fragile.

Sometimes we hear it in interviews: “Only X still works on that part, you’ll need to ask them” or “I tried touching that module once, but it’s too hard to understand.” Those are legacy warning bells.

Other times we see it in the git history: big commits that touch dozens of files for changes that should be simple. Or postponed upgrades like “we can’t move past version 16 of this framework because that component will break.”

And yes, outdated dependencies and hotspots in version control remain the classic signs.

We’ve found half of the early-stage companies we audit fall into the same trap: chasing features so fast that maintenance dies quietly in the corner. Unmanaged legacy code is one of the most common red flags we raise during our audit process.

What to do to avoid harmful legacy in your product?

Think of your codebase like a garden. You plant new things, it grows, it evolves. But if you don’t tend it, weeds creep in, roots tangle, and soon the whole thing is choking. Regular care is small, almost invisible. Leave it two years and you’ll need heavy machinery to clean it up.

Healthy and mature teams treat legacy the same way. Small maintenance blends into daily work: touch code, update dependencies, finish a feature, prune as you go. That’s culture.

But gardens also need bigger work from time to time. Large refactors, architectural upgrades, and structural fixes can’t be hidden in day-to-day work. They must be visible on the roadmap to get time, budget, and attention.

When culture isn’t enough, you need therapy.

  • Cooldowns after major releases.
  • Dedicated cleanup sprints.
  • In extreme cases, even a feature freeze.

No one likes it, but sometimes it’s shock treatment. The difference is whether leadership is pragmatic enough to admit it’s needed.

The easiest way to get non-technical founders on board? Quantify the pain. Show how much time bugs waste in a metric they care about: $$$. Show how much revenue slipped because the team couldn’t deliver fast enough. CFOs don’t argue with numbers.

How teams can spot and track legacy

Spotting legacy code

Tools like Aikido will tell you when dependencies are stale. SonarQube and Qodana highlight complexity. CodeScene even maps churn against bug reports. Tools don’t know your business but they’ll happily flag a scary module that hasn’t been touched in years. These are valuable maps.

The real tool however is human judgement: is this system harmlessly old, or dangerously fragile? That’s where a seasoned auditors and senior development teams earns their keep.

Tracking legacy code

Legacy isn’t static but it creeps. Mature teams keep an eye on it with heuristics: is this component still fit for purpose? Is it safe? Is it maintainable? Is it slowing us down? The answers change over time. Tracking means building in regular reviews, measuring DORA metrics to watch feedback loops, and revisiting technical vision before things rot in place.

Good teams also acknowledge that “development” is also about updates, tests, documentation, sharing knowledge, validating with product. All of that needs space in planning. If you’re not seeing it, legacy is already creeping in.

“We don’t have time for that”

Fair enough, you need features fast and time is limited. It’s the classic pain for almost every startup.

But we are entering the territory of technical debt now. If your challenge is “we don’t have time,” that’s debt, not legacy. And it requires a different playbook. There’s one thing we can highlight though.

Scoping properly is crucial for teams under real pressure to ship fast. If you can’t free up engineering time, gain it somewhere else. Strip back to the MVP. Get customer feedback early. Show progress with smaller slices, even if the first version can’t go live.

We’ve written a set of guides on managing debt and refactoring safely: