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MG Software.
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MG Software · Haarlem

Modernise legacy software

Outdated software costs more than you think: slow processes, security risks, high maintenance costs and the inability to add new features.

MG Software modernises your existing systems without stopping your business. We migrate step by step so your team can keep working.

Whether it is a PHP application from 2012, an Access database that runs the entire company, or a custom ERP built by an intern: we have seen it before and we know how to approach it.

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Does this sound familiar?

These are the most common signs your software needs modernisation.

Slow performance

Pages load slowly, queries take minutes, users complain about wait times that reduce productivity.

High maintenance costs

Every small change takes disproportionate effort because the codebase has become fragile and opaque.

Security risks

Outdated frameworks without security patches, known vulnerabilities that remain unresolved.

No room to grow

New features are impossible or take months. The architecture was not designed for what you need now.

Key-person dependency

There is one developer who understands the system, and when that person goes on holiday or leaves everything stops. No documentation, no tests, only implicit knowledge in the head of someone who might be gone tomorrow.

Compliance problems

Audits that fail because the system has no proper logging, no role-based access control, or runs on infrastructure that no longer meets current security standards. The longer you wait, the bigger the risk of fines or data loss.

Our approach to redevelopment

We do not replace everything at once. We modernise step by step so your business keeps running.

01

Audit

We analyse the current codebase, architecture, data model and bottlenecks. Result: a clear report with priorities.

02

Migration strategy

Which parts first? Strangler fig pattern or big bang? We choose the approach that fits your risk profile.

03

Incremental migration

We replace module by module, running old and new in parallel so both versions work side by side.

04

Data migration

Existing data is safely migrated with validation, mapping and fallback scenarios.

05

Validation & handover

Thorough testing, documentation and knowledge transfer to your team. Including maintenance agreements.

Modernisation strategies

There is no single right way to modernise legacy software. The choice depends on your risk tolerance, budget and time pressure.

Strangler fig (gradual)

Approach:

New functionality is built in the new system. Existing components are replaced one by one while the old system keeps running. A proxy layer routes traffic to the correct system.

Pros:

Minimal risk, immediate value per module, rollback is always possible. The business barely notices during the transition.

Cons:

Longer timeline, temporarily higher complexity from two systems running in parallel, and it requires discipline to actually phase out the old system.

Big bang (complete rewrite)

Approach:

The old system is fully replaced by a new system that launches in its entirety. All functionality is rebuilt and switched over at a single moment.

Pros:

Clean start without legacy compromises, optimal architecture from day one, no maintenance of two systems at the same time.

Cons:

High risk if scope is not tightly managed. Long period without visible results. If something goes wrong at launch, rollback is difficult.

Hybrid approach

Approach:

The core of the system is rebuilt, but less critical parts are first wrapped or connected rather than rewritten. Over time these parts are replaced too.

Pros:

Combination of speed and safety. The most important pain points are resolved quickly while the rest follows at a natural moment.

Cons:

Requires a good assessment of what is and is not critical. Without clear boundaries the hybrid model can become as complex as a strangler fig.

After the migration

The first weeks after a migration are when the investment becomes visible. Pages that used to take seconds now load in milliseconds. Deployment cycles that took weeks are reduced to hours. Your developers spend their time on new features instead of firefighting legacy code.

What we often see with clients who have completed a redevelopment is that the team itself becomes more productive and motivated. Working with modern tooling and an understandable codebase makes a big difference in job satisfaction. That translates directly into faster turnaround times and fewer errors.

We monitor the new application intensively in the first month after launch. That means alerting on errors, performance dashboards and weekly check-ins with your team. After that period we scale down to regular maintenance, unless continued development is planned.

Benefits of modernisation

After redevelopment your software is faster, more secure and easier to maintain. New features take less time, your team works more productively and you reduce the risk of costly incidents.

The investment pays for itself through lower operational costs and higher innovation speed. Most clients notice the difference within the first quarter after migration.

What we modernise

Redevelopment can mean many things. These are the most common project types we deliver.

Outdated web applications

PHP, jQuery, AngularJS or other frameworks that are no longer maintained. We migrate to React or Next.js with a modern architecture, better performance and a codebase your team can maintain without specialist knowledge of outdated technology.

Desktop to web

Windows applications built in .NET, Delphi or Java Swing that only run locally. We translate the functionality to a web application that is accessible everywhere, receives automatic updates and requires no installation on your employees workstations.

Spreadsheets to software

Excel files that have grown into business-critical systems with macros, VBA code and cross-references that nobody dares touch anymore. We extract the business logic and build a robust application with validation, multi-user support and an audit trail.

Monolith to microservices

One large application that does everything but where every change increases the risk of unexpected side effects. We split the monolith into independent services that can be deployed, scaled and maintained separately.

Investment and payback period

A redevelopment is a serious investment, and it is fair to want to know when it pays for itself. The exact timeline depends on your situation, but we see with most clients that savings on maintenance costs, fewer incidents and higher productivity recoup the investment within twelve to eighteen months.

What is often overlooked are the indirect costs of legacy software: longer onboarding of new employees who have to learn the old system, missed opportunities because features cannot be built, and the risk of data loss or security incidents that cause reputational damage.

We always prepare a business case for the redevelopment, with a realistic estimate of costs, savings and risks. No promises about exact ROI percentages, but an honest analysis that helps you make the right decision.

Technology

We migrate to modern, proven stacks.

React / Next.js

Web & frontend

React Native

Cross-platform mobile

Node.js / Bun

Backend & APIs

PostgreSQL

Relational data

Supabase

Auth, storage, realtime

Vercel / AWS

Hosting & CDN

Stripe / Mollie

Payments

OpenAI / LLMs

AI integrations

Why MG Software?

No middlemen

You talk directly to the developers working on your project. No project manager filtering or slowing information.

Ownership and transparency

You own the code. Repositories, credentials and documentation are handed over. No vendor lock-in.

Dutch team

Based in Haarlem with clients across the Netherlands. No timezone issues, no language barriers.

Full-stack, no loose ends

From database design to deployment: we deliver the full journey. No external UX agency or third-party QA needed.

Related pages

Discover our other services or read more about specific topics.

Custom developmentSoftware integrationsExamplesApp developmentBlogCalculator

Frequently asked questions

When is redevelopment better than rebuilding?

When the core logic is still valuable but technical debt is too high. Redevelopment preserves business knowledge and data while modernising the architecture. A full rebuild throws everything away, including proven logic.

How long does redevelopment take?

Depends on scope, but a typical engagement takes three to nine months. We work incrementally so you are not without a working system for months.

Can you modernise legacy systems?

Yes. We have experience modernising PHP, .NET, Java and other legacy stacks to modern architectures. The approach depends on the current state and your goals.

What happens to existing data?

Data migration is a core part of every redevelopment engagement. We validate, map and migrate data with thorough tests and fallback scenarios.

How do you minimise downtime?

By migrating incrementally: old and new systems run in parallel. Users barely notice the transition. We plan cutover moments carefully.

What does software redevelopment cost?

Investment depends on the size of the current system, desired modernisation and number of integrations. After an audit we provide a transparent estimate.

Can you modernise any programming language?

We have extensive experience with PHP, .NET, Java and Python. For less common languages we assess the situation and bring in specialists if needed. The key is understanding the existing logic, regardless of the language it is written in.

What if my original developer is no longer available?

That happens more often than you might think. We start by reverse-engineering the existing code and documenting what we find. This builds the knowledge needed to modernise the system safely, even when no original documentation is available.

How do you ensure users are not disrupted?

We run the old and new system in parallel during the transition. Users keep working while we migrate components one by one. The final switchover is planned at a quiet moment and tested extensively beforehand. If anything goes wrong we switch back immediately.

Is redevelopment always cheaper than building new?

Not necessarily. Sometimes technical debt is so severe that rebuilding is more efficient. That is why we always start with an honest audit. We tell you the best route, even if that means redevelopment is not the right choice.

What if we only want to modernise part of the system?

That works perfectly. We work modularly: you choose which components have priority and we modernise those first. The rest keeps running as is. This spreads the investment and delivers quick results where they are needed most.

How long do you stay available after delivery?

We offer maintenance retainers so you are not without support after delivery. We also transfer knowledge to your team through documentation and optional training. The duration and scope are agreed together, from a few months of aftercare to a long-term partnership.

Ready for a fresh start?

Let us analyse your current system. We give honest advice on whether modernisation is the right choice.

Request analysisView examples
MG Software
MG Software
MG Software.

MG Software builds custom software, websites and AI solutions that help businesses grow.

© 2026 MG Software B.V. All rights reserved.

NavigationServicesPortfolioAbout UsContactBlogCalculator
ServicesCustom developmentSoftware integrationsSoftware redevelopmentApp developmentSEO & discoverabilityAPI integrations
LocationsHaarlemAmsterdamThe HagueEindhovenBredaAmersfoortAll locations
IndustriesLegalEnergyHealthcareE-commerceLogisticsAll industries