Legacy systems continue to support core operations, but they come with a steep price. According to Gartner, companies are set to allocate around 40% of their IT budgets this year to managing technical debt, much of it tied to outdated applications.
In some organizations, particularly across the public sector, up to 80% of IT spending is consumed by maintaining aging systems. That level of investment leaves little capacity for innovation, modernization, or new development, making it difficult to move forward at a sustainable pace.
The greater risk lies in talent. When critical systems depend on a small group of specialists approaching retirement, the margin for error becomes uncomfortably thin. Modernization is not only about updating technology, it is about safeguarding continuity and ensuring the business can operate without disruption.
Modernization provides a practical path forward without the need to rebuild everything from the ground up. In this Altamira guide, you will see how it works, which strategies are worth considering, and how to manage risk throughout the process.
Top approaches to modernize legacy systems
Legacy modernization is no longer limited to system updates. It is driven by the need to meet the organization’s evolving digital demands. Businesses choose to modernize legacy applications for a range of practical reasons. By combining different modernization approaches, they can strengthen core IT and infrastructure, respond faster to change with relevant features and capabilities, improve operational efficiency, and deliver a better customer experience.
1. Re-platform / Rehost
This approach allows legacy applications to run in the cloud without significant changes to the core system. In some cases, selected parts of the code are adjusted, or the way the application interacts with the database is refined. It is often seen as a fast way to move away from MIPS (million instructions per second) consumption and start benefiting from cloud infrastructure. With partner solutions such as TmaxSoft, this type of modernization can typically be completed in under seven months.
2. Rewrite
Businesses turn to legacy modernization for several practical reasons, including:
• The rising cost of maintaining existing applications
• Monolithic codebases that are difficult to evolve
• Limited flexibility when adding new features
• A shrinking pool of specialists able to support and scale legacy technologies
Rewriting legacy languages can be approached either manually or through automated tools. Depending on the scope and complexity, these legacy modernization projects are typically completed within 9, 12, or 16 months.
3. Replace
In some cases, organizations choose to replace legacy applications with COTS (commercial off-the-shelf) products or SaaS solutions. This approach relies on ready-made platforms with predefined interfaces and workflows designed to integrate with existing systems and processes. Well-known examples include PAS (Policy Administration Systems) and platforms like Salesforce.
This option allows businesses to adopt modern development environments, meet evolving security and compliance requirements, and rely on applications that are easier to maintain and scale over time.
4. Retain
In some situations, organizations decide to keep their legacy systems in place despite the broader push for modernization. This choice is often driven by several factors:
• The system already delivers the required functionality without gaps
• Teams are familiar with how it operates and rely on established workflows
• Replacing it would require untangling deeply integrated dependencies across applications and business processes
• Data is primarily needed for audits or compliance, making full modernization unnecessary
In these cases, applications can be archived in lower-cost storage or adapted to generate reports when required, with a plan to phase them out over time.
5. DevOps for Legacy
As part of the modernization journey, many large mainframe-driven organizations consider adopting a unified DevOps approach as a practical step forward. Applying DevOps to legacy systems enables continuous integration of new or updated code into a central repository, helping ensure stable builds that can be deployed more reliably and without delay.
By introducing shared development environments, centralized code management, and automated testing, organizations create a solid foundation for modernization. This setup also makes it easier to deliver business changes in shorter, more manageable cycles.
6. Data Modernization for Legacy
For years, enterprise organizations—particularly in banking and financial services—have been dealing with the growing cost of maintaining legacy data stored in systems such as VSAM, ISAM, IDMS, and IMS. The priority today is to move that data into modern databases that can support greater agility, cloud adoption, and evolving data use cases.
By shifting to more scalable and flexible data platforms, businesses can better meet current demands without being constrained by legacy structures. With solutions built around technologies like Snowflake, along with proven migration accelerators, organizations can transition to modern RDBMS, NoSQL, and cloud-based environments more efficiently.
7. Legacy Optimization
An important step in the modernization journey is identifying opportunities to reduce mainframe MIPS consumption. Savings achieved through MIPS or batch optimization can then be redirected to support further modernization efforts.
This approach focuses on analyzing systems, subsystems, workloads, application code, and SQL performance to identify inefficiencies. With targeted optimization, organizations can typically reduce MIPS usage by 12–35% within three to six months, creating both immediate cost relief and room to invest in future improvements.
8. APIfication
Monolithic applications can be broken down into smaller, independent functions, exposed as services, and connected through APIs. This approach makes it easier to integrate systems across the organization and supports a more flexible, modular architecture.
With platforms such as MuleSoft, organizations can accelerate this transition and build systems that are easier to adapt over time.
Modernizing applications does not have to be disruptive or overly expensive. With the right approach, businesses can continue to get value from existing IT investments while gradually evolving their systems to meet future needs.
How to choose the right one: legacy system modernization approaches
Choosing a modernization strategy is a structured exercise that requires balancing risk, cost, and expected business value. It starts with a clear understanding of each system’s role, the level of technical debt it carries, and its overall complexity, then maps these factors to the most suitable approach using the “7 Rs” framework.
Step 1: Score each system by application modernization impact
Begin by assessing how modernization would affect each system. Use a straightforward checklist to evaluate every legacy application against six key factors, helping you establish a clear and consistent baseline.
When assigning ratings, use a scale from 1 to 10 for each factor. Systems that receive higher scores are typically stronger candidates for modernization.
Step 2: Map each system to the right “R”
Once a system has been scored, select the least disruptive option from the 7 Rs that still delivers meaningful improvement. This helps group systems by how much change they require and the value they continue to provide to the business.
Here’s a quick overview of the options and when they are most appropriate:
• Retain: When the system still meets business needs and disruption should be kept to a minimum
• Retire: When applications are outdated, duplicated, or already replaced by more relevant tools
• Rehost: When the goal is to move with minimal disruption and avoid major changes
• Replatform: When the core architecture remains sound but requires better system performance or compatibility
• Refactor: When reducing manual effort is a priority or the system has become difficult to maintain
• Re-architect: When long-term flexibility is needed to support evolving business models
• Replace: When legacy systems limit progress or no longer meet current technical expectations.
Step 3: Define limits and plan around them
Set clear boundaries around time, budget, and the level of disruption the business can absorb. Some teams take a gradual approach, refactoring systems over the course of a year, while others prioritize quick wins through rehosting to reduce infrastructure risk. The right balance depends on business urgency and any regulatory requirements.
When compliance or data sensitivity is a concern, it’s important to rule out cloud-first options early. At this stage, tools like Kodesage can help identify hidden risks, map system dependencies, and highlight what is worth modernizing before any changes are made to the codebase.
Step 4: Start small, then scale
Begin with a low-risk pilot by migrating a non-critical module or service and evaluating the results. This approach builds confidence and allows you to adjust the strategy before moving on to more complex systems. Many teams follow the “strangler pattern,” gradually replacing parts of a system instead of attempting a full transition at once.
Modernization delivers better outcomes when it is guided by data rather than assumptions. Scoring systems, aligning them with the right approach, and starting with smaller initiatives all help reduce risk. With a clear understanding of system structure, impact, and cost, teams are in a stronger position to make informed decisions.
The final words
Modernizing legacy systems can reshape how a business operates and improve overall efficiency. Updated systems deliver better performance, integrate more easily with modern technologies, and give organizations the flexibility to respond to changing market conditions.
One practical approach is lift-and-shift, often implemented using tools like the Charon emulator. This allows existing applications to run on modern infrastructure without significant code changes, reducing downtime and lowering the risks associated with full system replacement. It also creates a smoother path toward more advanced environments.
If you are considering modernization strategies, the right support can make a difference. A structured assessment of your current landscape helps identify the most effective next steps. Every organization operates differently, so the approach should reflect specific needs rather than follow a one-size-fits-all model.
What once supported the business now dictates what’s possible? Legacy application modernization is about regaining control. Get in touch to learn more.
