Assessment & Consulting
We audit the existing application, architecture, dependencies and infrastructure to understand what should stay, what needs to change and where modernization will have the biggest business impact.
Legacy Application Modernization Services
We provide legacy application modernization services that improve outdated architecture, infrastructure, integrations and codebases without disrupting the business logic that still works. Our end-to-end approach covers discovery, architecture, engineering, QA and migration, helping teams reduce maintenance costs, improve reliability and create systems that are easier to change and scale.
10years of software development experience
200+products delivered across web and mobile
67senior engineers across web, AI and mobile
90%of clients come back for a second project
01 — Services
Our Legacy Application Modernization Services
01
02
Reengineering & Refactoring
We restructure outdated code and remove technical debt without throwing away working business logic. We create a codebase your team can maintain, extend and release with confidence.
03
Application Rearchitecting
We replace rigid architecture with a structure that can scale and evolve. This can mean modularizing a monolith, introducing services where they make sense, or redesigning the application around clearer boundaries.
04
Cloud Migration
We move applications from aging infrastructure to modern cloud environments while accounting for data, integrations, security and operational continuity.
05
Integration Modernization
We introduce modern APIs and integration layers around legacy systems so they can work with newer applications, third-party services, CRMs, ERPs and data platforms without replacing the core immediately.
06
Data Modernization
We clean up, transform and move legacy data while preserving the information the business depends on. Migration is tested against the source system before production cutover.
02 — Industries
Legacy Application Modernization Services: Industries We Help
Logistics and Supply Chain
Upgrading legacy fleet, routing, tracking, shipment management, and supply chain systems.
Fintech
Modernization of legacy payment, KYC, financial operations, and account management systems.
Healthcare
Modernization of legacy patient platforms, healthcare workflows, data systems, and administrative tools.
SaaS
Revamping legacy cloud platforms, subscription systems, multi-tenant applications, and business workflows.
Retail Technology
Modernization of legacy POS, customer platforms, and retail operations systems.
Real Estate
Transforming legacy property platforms, listing management, tenant workflows, and real estate operations systems.
Why Companies Choose Rero for Legacy Application Modernization
Senior-only team
The engineers assessing your legacy system are the people who work on the modernization. There is no handover from a sales team to a different delivery team after the contract is signed.
Modernize what matters
We do not recommend a rewrite simply because the technology is old. If a component works, we look for ways to keep it. We focus the budget on the parts creating real technical or business problems.
Phased instead of disruptive
We modernize legacy systems in stages, reducing technical risk, preserving business logic and allowing your teams to continue operating while the underlying technology evolves.
One team from audit to release
Architecture, backend, frontend, DevOps and QA work as one senior team throughout the modernization process.
★★★★★
“RERO delivered a fintech marketplace platform end to end, increasing application submissions by 40%, reducing KYC processing time by 60%, and maintaining over 99% uptime. The team had smooth project management, met all deadlines, and responded quickly.”
1 / 4
04 — Process
How We Work on Legacy Application Modernization
01
Discovery & Technical Audit
We map the current architecture, codebase, integrations, infrastructure and data flows. We identify technical debt, critical dependencies and the areas creating the most risk.
02
Modernization Roadmap
We define what to refactor, rearchitect, migrate, replace or keep. You get a prioritized roadmap based on technical risk, business value and budget.
03
Architecture & Scope
We design the target architecture, migration approach and release strategy. At the end of the phase, you have a clear scope, implementation plan and fixed estimate.
04
Incremental Modernization
We modernize the system in controlled releases. Each stage delivers working improvements while the existing application continues supporting the business.
05
QA, Migration & Support
We test the modernized components against existing behavior, validate integrations and data, then release in stages with an option to continue maintenance and further modernization.
05 — Problems
Problems We Solve with Legacy Application Modernization
01
Nobody wants to touch the old code
Years of patches have made even small changes risky. We first map the system and its dependencies, then isolate the areas that need attention so modernization becomes a sequence of manageable changes.
02
Every release takes too long
Manual deployments, tightly coupled components and fragile environments make releases expensive. We improve architecture and delivery pipelines so teams can release smaller changes more safely.
03
We need new features, but the current system cannot support them
When the architecture has become the bottleneck, adding another feature only increases the problem. We create cleaner boundaries and modern interfaces so new functionality can be built without fighting the old system.
04
The infrastructure is expensive and difficult to maintain
Older hosting environments often require specialist knowledge and manual intervention. We assess what can move to modern infrastructure and choose a migration path based on the actual requirements.
06 — Why custom
Why Choose Legacy Application Modernization Services?
Modernization helps you extend the life of a system your business already depends on. We remove the technical limitations that slow down growth, releases and day-to-day operations.
Keep what already works
Your legacy system contains business logic, workflows and data built up over years. We preserve the parts that still work, modernizing the components that create problems.
Reduce technical debt
Replace fragile code, outdated dependencies and tightly coupled components with a cleaner architecture that is easier to maintain, test and extend.
Release changes faster
Modernize the architecture, development workflow and deployment process so your team can introduce new features without putting the entire application at risk.
Improve performance and reliability
Address slow processes, infrastructure bottlenecks and fragile integrations to make the application more stable, responsive and predictable as usage grows.
07 — Challenges
Key Challenges of Legacy Application Modernization and How Rero Overcomes Them
Challenge
Nobody fully understands the existing system
Years of undocumented changes, integrations and workarounds make the application difficult to assess.
How we handle it
Technical discovery before development
We inspect the architecture, code, dependencies, data flows and deployment process before recommending major changes, creating a modernization plan tailored to your system.
Challenge
Modernization could disrupt the business
The application may support revenue-generating or mission-critical processes that cannot simply be switched off.
How we handle it
Incremental releases and parallel operation
We break the work into controlled stages and introduce new components gradually. Old and modernized parts operate together until the transition is proven where needed.
Challenge
Nobody knows whether to refactor or rebuild
Some components are outdated but stable. Others are actively blocking growth.
How we handle it
Modernization decisions based on evidence
We assess each major component by business value, technical risk, maintenance cost and future requirements. Sometimes the right answer is refactoring. Sometimes it is rearchitecting or replacing one part entirely.
Challenge
Technical debt keeps coming back
A modernization project can improve the codebase without fixing the way changes are delivered.
How we handle it
Better architecture and engineering practices
We improve testing, CI/CD, environments, observability and documentation alongside the application itself, so the system stays maintainable after the project ends.
08 — Costs
Custom Legacy Application Modernization Costs
Ranges below are based on our own delivered projects and assume a European delivery team. The final scope, team composition and fixed price are defined through a paid discovery phase.
Legacy System Assessment & Modernization Plan
$8k–15k
- Architecture and codebase audit
- Technical debt assessment
- Modernization roadmap
- Infrastructure and security review
Full Application Modernization
$40k–90k
- Architecture modernization
- Replacement of outdated components
- Database and API modernization
- Performance and security improvements
Ongoing Modernization & Support
from $3k per month
- Incremental modernization
- Maintenance and security updates
- Performance monitoring
- New integrations and improvements
FDE rates are indicative and may vary based on the level of expertise and project requirements.
09 — Certifications
Certified to the highest standards
- ISO/IEC 27001
Information security management, audited annually.
- GDPR compliant
Data processing agreements and EU-hosted infrastructure on request.
- Clutch Top Developer
Verified client reviews, 4.9 average rating.
- HIPAA-aware delivery
Process and infrastructure for regulated healthcare products.
10 — Case studies
Our case studies
Trust and Review Signal Platform
An AI-powered Google Business Profile assistant that helps local businesses climb to the top of Google Maps.
AI Chat – Your AI assistant
AI chat app with voice input, document analysis, and image generation.
Sway AI Dance
App for transforming still images into AI dance videos.
Synchron Time Tracker
AI-powered platform for project management, time tracking, and team collaboration.
11 — FAQ
Frequently asked questions
How long does application modernization take?
A focused modernization can take a few months. Larger applications with multiple integrations, data migration and architecture changes can take more than six months. We define the scope and milestones after assessing the existing system.
Do you recommend rewriting a legacy application from scratch?
Not by default. A rewrite can make sense when the existing system is fundamentally unmaintainable, but it also means rebuilding years of business logic and edge cases. We first assess whether incremental modernization can deliver the result with less risk.
Can you move our legacy application to the cloud?
Yes. We can assess whether rehosting, replatforming, refactoring or a hybrid approach makes the most sense. The right strategy depends on the application's architecture, infrastructure, dependencies, security requirements and expected workload.
Can we start with an assessment only?
Yes. Discovery is a paid, standalone engagement. It gives you an assessment of the current system, modernization options, target architecture, prioritized roadmap and fixed estimate. You can use those deliverables whether or not you continue with Rero.
Who owns the modernized application?
You do. The source code, repository, infrastructure and documentation belong to you. Continuing support with Rero remains optional.
12 — Related
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Modernize the System Your Business Depends On
Tell us what is holding your current application back. We start with a technical assessment, identify the highest-risk areas and outline a practical modernization path.
Or write to info@rerotech.com