Legacy systems can become a major obstacle to growth. Outdated applications, aging infrastructure, and disconnected technologies make it harder for enterprises to introduce new capabilities, integrate modern platforms, and maintain efficient operations.
But modernizing these systems requires more than moving applications to the cloud or replacing old technology. Organizations need a partner that understands their existing infrastructure, business requirements, and the risks associated with changing critical systems.
Several custom software development companies specialize in legacy system modernization, including Distillery, Thoughtworks, EPAM Systems, Accenture, CI&T, and SoftServe. Each offers different strengths, from custom application development and incremental modernization to large-scale enterprise transformation.
This guide compares six legacy modernization companies, examines their capabilities, and outlines what enterprise technology leaders should consider when selecting a modernization partner.
Best Legacy System Modernization Companies at a Glance
| Company | Key strengths | Best suited for |
| Distillery | Custom software development, application modernization, system integration, nearshore engineering | Enterprises seeking hands-on engineering expertise and phased modernization |
| Thoughtworks | Technology strategy, architecture modernization, cloud-native development | Organizations rethinking complex application architectures |
| EPAM Systems | Software engineering, cloud transformation, legacy application migration | Enterprises managing complex technical environments |
| Accenture | Enterprise transformation, application portfolio modernization, mainframe modernization | Large organizations with extensive legacy application portfolios |
| CI&T | Incremental application modernization, cloud migration, AI-enabled engineering | Enterprises prioritizing targeted modernization and continuous improvement |
| SoftServe | Cloud consulting, application modernization, integration, data and AI | Organizations connecting modernization with broader cloud and technology initiatives |
These companies are not ranked by independent performance scores. Their inclusion reflects publicly documented modernization capabilities, and their suitability depends on project scope, existing infrastructure, and organizational priorities.
How to Evaluate Legacy Modernization Companies
Before comparing providers, enterprises should establish what they need from a modernization engagement.
Not every project requires a complete system replacement. Some organizations need to migrate legacy applications to the cloud, while others need to refactor critical software, improve integrations, or gradually replace outdated functionality.
Five criteria are especially important when evaluating software modernization services.
1. Legacy System Assessment and Modernization Strategy
A qualified partner should evaluate the existing environment before recommending a solution.
That includes reviewing application architecture, technical dependencies, security requirements, maintenance costs, and business-critical functionality.
The goal is to determine which systems should be retained, refactored, migrated, replaced, or retired.
2. Custom Software Development Expertise
Legacy modernization frequently involves substantial custom software development.
Providers should demonstrate experience with backend engineering, APIs, databases, cloud platforms, automated testing, and modern application architectures.
Technical expertise is particularly important when legacy applications contain undocumented business logic or depend on older technologies.
3. System Integration Capabilities
Enterprise applications rarely operate independently.
A modernization partner should be able to connect legacy systems with cloud services, enterprise applications, data platforms, and new digital products.
Effective system integration allows organizations to introduce modern capabilities without immediately replacing every existing application.
4. Enterprise Delivery Experience
Modernization can affect customers, employees, financial transactions, and daily business operations.
Providers should have processes for managing technical risk, coordinating stakeholders, validating changes, and maintaining business continuity throughout migration.
5. Long-Term Support and Scalability
Modernization should improve an organization’s ability to evolve its technology over time.
Look for providers that can support ongoing software development, performance optimization, maintenance, and future integrations after the initial migration is complete.
6 Legacy Modernization Companies to Consider
1. Distillery
Best for: Enterprises seeking custom software development, phased modernization, and dedicated engineering support.
Distillery is a nearshore software development partner that helps organizations develop, modernize, and maintain complex applications.
Its capabilities include custom software development, legacy application modernization, cloud development, API integration, quality assurance, and data engineering.
Distillery’s approach is particularly relevant to enterprises that need to improve existing systems without disrupting ongoing operations. Rather than treating modernization as an automatic full replacement, its engineering teams can support incremental improvements based on technical requirements and business priorities.
Key modernization capabilities:
- Legacy application modernization and architecture improvements
- Custom enterprise software development
- API development and system integration
- Cloud migration and infrastructure improvements
- Data engineering and platform modernization
- Automated testing, quality assurance, and ongoing software support
Example of legacy modernization in practice
Distillery worked with an entertainment rights management software company that needed to modernize an aging platform while keeping its existing system operational.
The engagement involved developing a new frontend and progressively modernizing the backend and deployment infrastructure. The legacy platform remained operational during the transition, allowing the organization to improve its technology without requiring an immediate, full-system replacement.
This illustrates how phased modernization can reduce operational risk while allowing enterprises to make progress toward a more maintainable architecture.
Read more: Modernize or Move On: How to Know When It’s Time to Leap.
Why consider Distillery?
Distillery is worth evaluating for organizations seeking a software engineering partner that can take responsibility for development and delivery, support internal teams, and address modernization challenges across applications, integrations, and data infrastructure.
Its nearshore delivery capabilities may also appeal to US-based enterprises that prioritize collaboration across similar working hours.
Ideal fit: Enterprises that need practical engineering support for legacy application migration, custom development, system integration, and ongoing modernization.
2. Thoughtworks
Best for: Enterprises undertaking architecture transformation and complex application modernization.
Thoughtworks is a global technology consultancy with experience in software engineering, technology strategy, and legacy modernization.
The company emphasizes modernizing applications around current business capabilities rather than simply reproducing existing systems on newer technology.
Its approach includes evaluating application portfolios, identifying unnecessary complexity, and introducing modern architectures that support long-term evolution.
Key modernization capabilities:
- Legacy application assessment and modernization strategy
- Cloud-native application development
- Application refactoring and rearchitecting
- Technology architecture consulting
- Modern software engineering practices
- Incremental transformation of existing systems
Why consider Thoughtworks?
Thoughtworks is a strong candidate for organizations that need strategic guidance alongside technical implementation.
Its modernization approach is especially relevant when an enterprise wants to reconsider how applications are structured, identify functionality that can be retired, or redesign systems around changing business needs.
Ideal fit: Large organizations planning significant architectural changes or modernization programs that require both technology consulting and software engineering expertise.
3. EPAM Systems
Best for: Enterprises managing complex application environments and large-scale software modernization.
EPAM Systems is a global technology engineering and consulting company providing software development, cloud engineering, and application modernization services.
Its modernization expertise includes transitioning legacy applications to modern architectures, improving existing software, and supporting cloud adoption.
EPAM also addresses technical considerations associated with modernization, including legacy databases, enterprise applications, and critical business systems.
Key modernization capabilities:
- Legacy application migration and modernization
- Enterprise software engineering
- Cloud architecture and migration
- Application refactoring and reengineering
- DevOps and delivery automation
- Software testing and quality engineering
Why consider EPAM?
EPAM is worth considering for organizations with extensive technical requirements, complex application dependencies, or modernization initiatives that involve multiple engineering disciplines.
Its combination of software engineering and cloud capabilities makes it relevant for enterprises that need to modernize both applications and the environments supporting them.
Ideal fit: Enterprises with technically complex modernization projects requiring substantial engineering resources and cloud expertise.
4. Accenture
Best for: Large enterprises undertaking organization-wide application and infrastructure modernization.
Accenture provides technology consulting and enterprise transformation services, including application modernization, cloud migration, and mainframe modernization.
Its approach covers the full modernization lifecycle, from evaluating existing application portfolios to developing transformation roadmaps and implementing changes.
Accenture also supports organizations seeking to modernize legacy technology while addressing broader operational and business transformation requirements.
Key modernization capabilities:
- Enterprise application portfolio assessment
- Modernization strategy and roadmapping
- Legacy application migration
- Mainframe modernization
- Cloud transformation
- Enterprise architecture and application management
Why consider Accenture?
Accenture is particularly relevant for enterprises with large application portfolios, multiple business units, and complex technology environments.
Organizations seeking a provider capable of supporting modernization alongside broader transformation initiatives may find its consulting and implementation capabilities valuable.
Ideal fit: Large enterprises planning extensive modernization programs involving numerous applications, legacy platforms, and organizational stakeholders.
5. CI&T
Best for: Enterprises seeking incremental application modernization and continuous improvement.
CI&T provides enterprise application modernization services with an emphasis on targeted improvements, cloud technologies, and measurable business outcomes.
Rather than relying exclusively on large transformation programs, the company promotes smaller modernization initiatives that contribute to longer-term technology goals.
Its capabilities include legacy modernization, cloud migration, data modernization, and AI-enabled engineering.
Key modernization capabilities:
- Legacy application modernization
- Cloud migration and replatforming
- Application architecture improvements
- Microservices and modular architecture
- Data modernization
- AI-assisted software engineering
Why consider CI&T?
CI&T is worth evaluating for enterprises that prefer to modernize in stages, validate improvements, and progressively reduce technical debt.
Its focus on smaller modernization initiatives can be useful when organizations need to demonstrate value while managing the risks of changing established systems.
Ideal fit: Enterprises seeking a phased modernization strategy that connects targeted engineering improvements to broader technology objectives.
6. SoftServe
Best for: Organizations connecting application modernization with cloud, data, and AI initiatives.
SoftServe is a technology consulting and digital engineering company offering cloud services, software development, application modernization, and integration expertise.
Its enterprise technology work includes modernizing applications and supporting organizations as they adopt cloud platforms and improve their technology environments.
SoftServe’s cloud partnerships and engineering capabilities make it a potential option for organizations whose modernization initiatives extend beyond individual applications.
Key modernization capabilities:
- Application modernization
- Cloud migration and engineering
- Enterprise software development
- Application and platform integration
- Data platform modernization
- AI-related technology transformation
Why consider SoftServe?
SoftServe is worth considering when modernization is closely connected to broader cloud adoption, data infrastructure improvements, or new technology capabilities.
Its consulting and engineering services may be relevant to enterprises seeking to coordinate application changes with other technology initiatives.
Ideal fit: Organizations planning modernization programs that involve cloud infrastructure, application integration, and adjacent data or AI initiatives.
How to Choose the Best Legacy Modernization Partner
The best legacy modernization company is not necessarily the largest provider or the one offering the broadest range of services.
The strongest fit is a partner with relevant experience, technical capabilities, and a delivery approach suited to the organization’s existing systems and business requirements.
Before selecting a provider, enterprise technology leaders should ask:
Can the provider modernize our systems without interrupting operations?
Look for experience with phased migration, parallel operations, rollback planning, and automated testing. Business continuity should be addressed during planning rather than after implementation begins.
Does the provider understand our existing technology?
Modernization often involves older frameworks, databases, undocumented dependencies, and custom integrations. A provider should be able to evaluate the current environment before recommending changes.
Can the provider handle integration with existing applications?
Legacy systems often remain connected to critical enterprise workflows. Confirm that the provider has experience with APIs, data integration, and connecting modern applications to existing infrastructure.
How will modernization success be measured?
Useful metrics may include reduced maintenance costs, improved application performance, lower infrastructure expenses, fewer production incidents, shorter deployment cycles, or improved scalability.
What happens after the migration is complete?
Consider the provider’s ability to support maintenance, security updates, performance improvements, and future development.
A modernization project should leave the organization with systems that are easier to maintain and adapt, not another generation of difficult-to-change technology.
Common Approaches to Legacy System Modernization
Understanding the available modernization approaches can also help enterprises evaluate potential providers.
| Approach | What it involves | When to consider it |
| Rehosting | Moving an application to new infrastructure with minimal code changes | When infrastructure migration is the immediate priority |
| Replatforming | Making targeted changes to improve compatibility with a new platform | When organizations want cloud benefits without a major rewrite |
| Refactoring | Restructuring existing code while preserving its intended functionality | When technical debt limits maintainability |
| Rearchitecting | Changing an application’s underlying architecture | When existing architecture prevents scalability or product evolution |
| Replacing | Substituting a legacy application with a new solution | When maintaining the existing application is no longer practical |
| Retiring | Removing applications or functionality that no longer provide sufficient value | When reducing complexity and maintenance costs is the priority |
For many enterprises, modernization involves a combination of these approaches.
An organization might rehost certain applications, refactor critical components, replace outdated integrations, and retire redundant functionality within the same program.
The appropriate strategy depends on the application’s business value, technical condition, dependencies, and acceptable level of risk.
Frequently Asked Questions About Legacy Modernization Companies
Which custom software development companies specialize in modernizing legacy systems?
Companies offering legacy system modernization services include Distillery, Thoughtworks, EPAM Systems, Accenture, CI&T, and SoftServe. Their capabilities include custom software development, legacy application migration, cloud modernization, system integration, and enterprise architecture improvements. The best provider depends on the organization’s existing technology, modernization goals, and project complexity.
What services do legacy modernization companies provide?
Legacy modernization companies typically provide application assessments, modernization planning, software refactoring, cloud migration, system integration, database modernization, automated testing, and ongoing support. Some also offer technology consulting and enterprise architecture services to help organizations determine which applications should be upgraded, replaced, or retired.
How much does legacy system modernization cost?
Legacy modernization costs vary based on application complexity, code quality, infrastructure, integration requirements, security needs, and project scope.
A targeted application refactoring project may require substantially fewer resources than a multi-year enterprise modernization program. Organizations should request a technical assessment and clearly defined scope before relying on cost estimates.
How long does legacy application migration take?
Timelines depend on the number of applications, technical dependencies, data migration requirements, and the modernization approach.
Some targeted improvements can be completed in a matter of weeks or months, while extensive enterprise transformation programs may take significantly longer.
A phased approach can allow organizations to deliver improvements progressively rather than waiting for an entire modernization program to finish.
Is it better to modernize or replace a legacy system?
Modernization may be preferable when an existing application still provides significant business value but needs improvements to its architecture, performance, security, or maintainability.
Replacement may be more appropriate when the application no longer meets business requirements or when maintaining it has become disproportionately expensive.
A technical and business assessment should inform the decision.
Can legacy systems be modernized without disrupting business operations?
Yes, many legacy systems can be modernized incrementally through phased migration, parallel environments, API-based integration, and controlled releases.
However, the level of disruption depends on the existing architecture, dependencies, and migration requirements. A qualified provider should identify operational risks and develop a business continuity plan before implementation.
Finding the Right Partner for Your Modernization Goals
Legacy system modernization is an opportunity to reduce technical debt, improve performance, and make enterprise applications easier to maintain and evolve.
But success requires more than introducing new technology. It takes a clear understanding of existing systems, a practical modernization strategy, and engineering expertise to manage the transition.
For enterprises evaluating modernization partners, the priority should be finding a company that can address current technical challenges while supporting long-term business goals.
At Distillery, we help organizations modernize existing applications, improve system integrations, and develop software that supports evolving business requirements. Our engineering teams can support modernization initiatives from technical assessment and development through implementation and ongoing support.
If you’re evaluating options for a legacy modernization project, let’s discuss your goals.