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Applications

Application Modernization

Modernize applications with security built in from the start.

Frustrated by the rising operating expenses and opportunity costs of your legacy applications? The burden compounds as maintenance becomes more difficult, security exposures grow, and releases lag. Limited resources are consumed by keeping the lights on, leaving too little time for growth and innovation.
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Tech debt: a tax that holds you back

Every application your business runs was built for a moment in time. Some have aged well, but many haven’t. When that gap goes unaddressed, you pay more in cloud bills, security exposure, lost productivity, and missed market opportunities.

By the time this gap emerges as a business problem, there are usually strategic implications: a core platform that won’t scale to support an acquisition. A revenue-critical application that can’t pass an audit. Releases that once took days but now consume weeks.

 

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The OnX approach

Find the right path for each application.

There is no universal way to modernize. Some applications are good candidates for a lift-and-shift to the cloud. Some need a deeper rewrite to take advantage of cloud-native services. Some need to be fully replaced. Yet others are worth modernizing in place because they still deliver value.

OnX assesses every application’s business value, technical condition, security posture, and dependencies. Then we recommend the path that delivers the best outcome at acceptable risk. That portfolio-aware approach is part of how OnX builds stronger foundations for our clients. 

 

Application Modernization capabilities

 OnX modernization engagements range from targeted replatforming
to complete rebuilds. Every engagement starts with a vigilant assessment.

Application Portfolio Assessment


A structured diagnostic of your current application landscape (including condition, cost, risk, business value, and dependencies) that produces a clear, defensible roadmap on where to focus modernization investment first.

Rehost & Replatform (Cloud Migration)


Migrations of applications to cloud infrastructure with the right level of change. That ranges from a straight lift-and-shift to targeted replatforming that captures cloud-native cost and performance gains without a full rewrite.

Refactor & Re-architect


Structural code changes that improve performance, scalability, and maintainability, typically used to bring an application onto modern frameworks, decouple monolithic architectures, or prepare a system for cloud-native services.

Rebuild & Replace


Full rebuilds of applications whose underlying architecture can’t be salvaged or where a replacement platform delivers the business outcome at lower long-term cost. OnX engineers the new platform, and the business gets a clean foundation to build on.

Legacy Application Patching & Hardening


For applications that need to stay in place, we deliver source code remediation, library upgrades, security patching, and the QA discipline to release the changes safely. This is often the right option for systems that work but carry unacceptable security or compliance exposure.

Integration & API Modernization


Modernize how legacy applications talk to the rest of your environment, wrapping legacy systems in modern APIs, replacing brittle point-to-point integrations, and creating the integration and security layer that makes the rest of the portfolio possible to evolve.

Where to start

Advisory engagements

A OnX advisory is a time-bound, fixed-fee engagement designed to give you a clear answer to a specific strategic question — fast.  

Workload Placement & Optimization Advisory

Best for: The OnX Workload Optimization & Placement Advisory delivers a workload-by-workload cost model, evidence-based placement analysis across every infrastructure option, and a funded roadmap your CFO can sign. Delivered in only weeks as opposed to months.

What you hold at the end:

  • A complete workload inventory with dependency mapping 

  • Framework-aligned cost and usage baseline and performance profiles per workload 

  • A FinOps maturity heatmap 

  • Documented compliance 

  • A prioritized roadmap for migration and optimization opportunities 

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What success looks like

Three outcomes show up most consistently. 

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Cost optimization

Lower run costs, lower licensing exposure, and lower maintenance overhead. Modernization can shave application maintenance and run costs by as much as 30% to 50%, freeing capacity to invest in what the business needs to build next.

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Reduced risk

 Security and compliance posture strengthened by design. Legacy systems running unsupported dependencies are systematically remediated, and the architectural patterns of the modernized environment simplify ongoing risk management.

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Operational efficiency

Organizations that complete modernization commonly achieve 40% to 60% faster release cycles, turning the application portfolio from business constraint to growth and innovation lever.

“Business is always chasing the next new thing — more features, new functionality. Tech debt gets ignored until security or other limitations force the issue. By the time someone asks us to modernize, it’s like raising a house: You can’t lift one corner. The whole structure has to come up together. The teams that do this well plan for it, and that’s exactly where we focus.”

Ari Steinberg

Ari Steinberg

 Delivery Director – Application Development 

Don’t take our word for it

“I love the creative, tailored solutions that are delivered in a consistent and reliable way while always doing what it takes to make things right.”

Chief Technology and Information Security OfficerFinancial Services / Banking

“My team at OnX have been trusted partners for a long time. They provide excellent technical support and pre-sales work. Their breadth of knowledge and ability to bring in the right resources have helped us steer our technology into the future.”

Managing Director, CISO, Head of TechnologyPrivate Equity / Financial Services

“OnX treats us like a partner and not just a customer. The technical expertise is next to none and the relationship management is some of the best I have experienced.”

Director, Telecom and Architecture ServicesHealthcare

Modernization is one part of the application lifecycle.

Most application modernization programs touch new development and ongoing management. OnX supports the full application lifecycle.

Related insights 

Frequently asked questions 

How does OnX approach application modernization? We help organizations update their existing applications to drive better business outcomes. That may mean migrating them to the cloud, rebuilding them on modern platforms, refactoring code to improve performance and maintainability, or patching and hardening systems that need to stay where they are. We always lead with an outcomes lens and align our recommendations to reduce the cost, risk, and operational drag that legacy applications place on the business.
Can OnX support the 4 Rs of application modernization? Yes, OnX helps clients tackle the 4 Rs of application modernization: rehost, replatform, refactor, and rebuild. Rehost is a straight lift-and-shift to new infrastructure, typically the cloud, without changing the code. Replatform makes targeted changes to take advantage of cloud-native capabilities. Refactor restructures the code itself to improve performance, scalability, and maintainability. Rebuild replaces the application entirely. Most portfolios end up with a mix of all four plus retain (leave it alone) and retire (decommission it).
How do you decide which applications to modernize first? OnX scores each application across four dimensions: business value, technical condition, security and compliance risk, and dependencies on the rest of the environment. Applications that combine high business value with significant operational drag or unacceptable risk tend to rise to the top. We also consider sequencing. Certain applications need to be modernized first because the rest of the portfolio depends on them. The Discovery & Design Workshop is designed to help answer this question.
How does application modernization improve security? Legacy applications frequently carry technical debt in the form of outdated libraries, unpatched vulnerabilities, and architectures that predate current threat models. Modernization — especially to cloud-native environments where identity management, encryption, and policy enforcement are built in — typically produces a materially stronger security posture. OnX treats security as a design input. We surface vulnerabilities during assessment, shape the architecture with secure design patterns, and run automated code reviews and security testing throughout the development lifecycle.
How is the OnX approach to application modernization different? Three things distinguish how OnX engages on modernization. First, we assess every application against business value and technical condition before recommending a path. Second, we cover the full set of modernization options (rehost, replatform, refactor, rebuild, integrate, patch), so our recommendations aren’t shaped by the limits of what we offer. Third, the team that modernizes an application can continue supporting it in production through OnX Application Management & Support. That way, the institutional knowledge built during the modernization stays with the application after go-live.

Strong foundations start with knowing what to fix first.

Every legacy application has a cost. OnX helps you determine which applications are costing
the most and which ones, modernized in the right order, will free your business to build what’s next.