Solution
Legacy system modernization
The old system still works, and the business depends on it. That is exactly why it is hard to touch. We modernize in stages, so each step leaves the business running and a little safer than before.
- 1,200+ clients helped
- Building since 2010
- 15 services, one team
- 50+ technologies
At a glance
What we build
We update or replace old business software in stages, so it can be changed safely, supported, and connected to the tools you use now, while the business keeps running.
Problems we solve
The software still runs the business, but it is hard to change, tied to old servers, understood by few people, and getting riskier every year.
Who we serve
Owners and technology leads of long-running business systems, and teams told that a platform or server is reaching the end of its support.
How to choose
Move in stages: first make the system safe and understood, then connect it, then replace it piece by piece. Choose a full rewrite only when the old system has nothing worth keeping.
The problem
Why old software becomes a risk
Software does not wear out, but its surroundings do. The language version stops receiving security fixes. The server is no longer sold. The person who understood the code leaves. A new tool cannot connect to it. Each year the cost of any change goes up, and each year the cost of a failure goes up too.
The usual reaction is to put it off, because the system works and a replacement sounds like a large, risky project. That instinct is partly right. A full rewrite is slow and often fails to reproduce rules the old system carried silently.
The better answer is neither to leave it nor to replace it in one go. It is to reduce the risk first, then change it a piece at a time.
How we solve it
A staged route out of a legacy system
A sequence of 5 steps. Understand it: Find out what it does, who depends on it, and where the risk lies.; Make it safe: Back it up, patch it, and add tests around the parts that matter.; Connect it: Put a clean interface in front, so new tools can use its data.; Replace one slice: Rebuild one function at a time and switch over when it is proven.; Retire the old parts: Switch off what is replaced, keep what earns its place..
- Understand itFind out what it does, who depends on it, and where the risk lies.
- Make it safeBack it up, patch it, and add tests around the parts that matter.
- Connect itPut a clean interface in front, so new tools can use its data.
- Replace one sliceRebuild one function at a time and switch over when it is proven.
- Retire the old partsSwitch off what is replaced, keep what earns its place.
- Systems we build
- Custom Software SystemsOperations PlatformsIntegration Platforms
- Often built with
- PHPJava.NETPythonTypeScript
Which route
Where does your system sit?
These four situations cover most of the systems we are asked about.
Which describes your system best?
Choose this when
Every change is slow and frightening, and only one or two people dare touch it.
- What you get
- A review, tests around the key parts, and a clean interface so new features can sit beside it.
- Keep in mind
- Plan to reduce the dependence on those one or two people at the same time.
Choose this when
An old server, database, or language version with a deadline.
- What you get
- A move to a supported platform, usually in stages, with the deadline respected.
- Keep in mind
- Start early. A forced move under deadline costs more than a planned one.
Choose this when
Staff re-type data because the system has no way to share it.
- What you get
- An integration layer that exposes the data safely to the tools that need it.
- Keep in mind
- Fix the data quality as you connect, or you will share the errors.
Choose this when
The business has changed and the software forces workarounds.
- What you get
- A redesign of the parts that matter, rebuilt a slice at a time.
- Keep in mind
- Agree what stays the same, so the move does not become a different project.
Routes
Five routes, and when each fits
Keep and look after it
Suits
A stable system with few changes needed and a person who understands it.
- Trade-off
- The risk stays, and the cost of change keeps rising.
Put a clean interface in front
Suits
A system whose data is valuable but whose screens and rules are hard to change.
- Trade-off
- The old core remains, so its age is hidden, not removed.
Move it piece by piece
Suits
Most business systems: the old and the new run side by side while functions move across.
- Trade-off
- Takes longer than a switch, and needs discipline to finish.
Rebuild it
Suits
A system whose design no longer fits the business at all.
- Trade-off
- The largest cost and risk, since hidden rules must be rediscovered.
Replace it with a product
Suits
Standard needs that a maintained product already meets.
- Trade-off
- You adapt to the product, and data must be moved with care.
How we do it
A staged modernization, step by step
Review and risk
We read the system, list the dependencies, and rank the risks by how likely and how costly each is.
What it produces
- System inventory
- Ranked risk list
Stabilize
Backups, patches, monitoring, and tests around the parts that carry the most business weight.
What it produces
- Test set
- Monitoring
Connect and extend
A modern interface goes in front, so new features and new tools no longer need to change the old core.
What it produces
- Interface layer
- Data checks
Move slice by slice
Each function is rebuilt, run beside the old one, compared, and switched over only when the results match.
What it produces
- Rebuilt slice
- Comparison report
- Switch plan
Worth knowing
What makes a modernization fail
Projects rarely fail on technology. They fail on what nobody wrote down, and on trying to do everything at once.
- Rules that lived only in the code or in one person's head
- A switch-over date with no way back
- Data moved without checking it row by row
- A new system that copies the old problems
What you get
What a modernization delivers
Understanding
- A written picture of what the system does and why.
- A ranked list of risks, with a cost for each route.
Safety
- Backups you have tested, patches applied, and monitoring that alerts.
- Tests that protect the behavior you rely on.
Progress
- Working slices delivered one at a time.
- A switch-over plan with a way back for each step.
Independence
- Documentation and handover, so you are not dependent on one person, or on us.
- A choice of ongoing care, at your discretion.
Technical depth
Techniques we use on old systems
The detail a technical reviewer will ask about: characterization tests, incremental replacement, data, and platforms.
Before changing old code, we record what it does with real inputs and write tests that pin that behavior. The tests tell us when a change alters something it should not.
- A routing layer sends each function to the old or new implementation, so functions move one at a time.
- Old and new results are compared on live traffic before the switch.
- Each move can be reversed by changing the routing, not by redeploying.
- Schemas are documented and migrated with scripts that can be re-run and checked.
- Row counts, totals, and sampled records are compared between old and new.
Common questions
Questions about modernizing old software
Do we need to rewrite the whole system?
Rarely. A staged move keeps what works and replaces what does not. A full rewrite is reserved for systems with nothing worth keeping.
Can the business keep running during the move?
Yes. That is the point of a staged route. The old and new parts run side by side, and each function is switched over only when it has been proven.
What if nobody understands the old code?
That is common. We start by recording what the system actually does, and we write tests that capture it, before we change anything.
How do we know what it will cost?
After the review, we cost each route in plain terms, with the first stage priced separately so you can start without committing to all of it.
Is it better to buy a product instead?
Sometimes. If your need is standard, a maintained product can be the cheapest answer. We say so when we see it.
Have a different question?
Tell us what you are weighing up and we will answer it plainly.
Ask a questionAlready a client? Email support@dechytech.com
Tell us about the system
Describe what it does, how old it is, and what worries you. We will review it and recommend a staged route, with the first step costed.