Legacy modernization
Introduction to Legacy Modernization with Low-code Platforms
Rano Salieva
February 28, 2025
In a nutshell
Legacy systems are outdated but essential technologies crucial for business operations. They are known for their reliability and revenue generation but are often expensive to maintain and may not meet performance standards.
Legacy modernization involves updating these systems to meet technological advancements and business needs. Strategies range from minor updates to complete overhauls.
Low-code platforms, such as ondeva Low-Code, offer a new approach to legacy modernization. They allow businesses to update systems with minimal coding. ondeva enables the creation of modern web interfaces, addressing digitalization challenges and making it a viable solution for legacy modernization.
What is a Legacy System?
Legacy systems are old systems that constitute the core of the business and have proven to work correctly in the production environment for decades. Some developers point out that legacy systems need to fit into the organization's technology goals. So, legacy systems are business systems that resist modification but are critical for a business to maintain.
Do programming languages determine whether a system is legacy or not? Engineers are divided on that. However, some programming languages might indicate a legacy system. These are COBOL, Assembler, PL/I, Visual Basic, and RPG.
Legacy systems typically have the following characteristics:
- They are critical for the business and generate revenue. An old but not business-critical system will not reach the status of a legacy system.
- They are built on stable and proven technology. Legacy systems are built on stable technology that can run 24/7.
- They are reliable, and possible bugs and errors have been fixed so that they can perform specified functions without problems.
Despite these positive characteristics, legacy systems are rarely described as high-performing. They can be high-performing, but their performance is usually low.
Legacy systems are expensive to maintain despite their business value. For example, in fiscal year 2019, the US government spent over $90 billion on IT, of which 80% was used to operate and maintain legacy systems. The UK government spends £2.3 billion a year on maintaining some 30-year-old legacy systems.
Legacy Systems Structure
Legacy systems are not only software. Their components include people, expertise, hardware, data, business processes, and approaches to software maintenance and development. Even though developers often talk about legacy in light of software systems, research favors a blended approach to legacy systems where organizational and technical concepts are intertwined and applied iteratively so that tech can be tested against business needs.
What is Legacy Modernization?
Legacy modernization is one of the three stages of the software lifecycle: maintenance, modernization, and replacement.
Maintenance
Involves small changes, such as bug corrections, that support the system in its current state. Usually, maintenance efforts are not enough to sustain a competitive advantage, and the cost of maintaining legacy systems increases with time.
Replacement
Used with systems that can’t be modernized due to costs and feasibility. It is usually used with systems that are undocumented, outdated, and not extensible.
Replacement is very resource-intensive, especially if most developers are busy performing maintenance tasks. It also requires intensive testing, and there is no guarantee that the new system will be better than the legacy system.
Legacy modernization
Attempts to evolve a legacy system when other software practices, such as maintenance and enhancement, fail. While maintenance efforts support the system for some time, eventually, they fall behind business needs.
Modernization includes more than maintenance; it changes a significant part of the legacy system and includes system restructuring or functional enhancements.
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Why Legacy Modernization?
As surveys suggest, developers turn to legacy modernization for the following reasons:
To remain agile to change
Most developers think legacy systems must be more flexible to respond to changing business needs. As customers want shorter time-to-market, legacy systems built on old programming languages become obsolete.
High maintenance cost
When maintenance costs become too high, developers start considering legacy modernization. The cost comparison between standard system maintenance and legacy system maintenance is a major driver of change.
Risk of failure
Legacy systems are perceived as prone to failure despite being reliable. The risk of failure is associated with a lack of experts who can support the system. Once the experts are unavailable, the legacy system becomes prone to failure.
Lack of knowledge
Over 90% of IT developers and engineers pointed out that a lack of resources causes legacy modernization. This issue is partially emphasized by the fact that experts in legacy systems are either retiring or leaving their jobs.
Real-life example:
In 2020, a crisis broke down in the unemployment systems in New Jersey and Connecticut. In the wake of the coronavirus pandemic, the states were flooded with unemployment claims that could not be processed.
The state had to release a plea to find COBOL developers to solve the issue, as their legacy system was built on COBOL. Some of these developers already retired but had to step up as volunteers to fix the system. Another example is the 2021 Superior Welding Supply company case, which also involved looking for a COBOL developer since their in-house developer died just before the company’s software crash.
Legacy Modernization Strategies
There are many legacy modernization strategies. Here are the 5 legacy modernization strategies:
- Replace
A strategy for legacy systems with low business value and quality. These systems can be replaced with generic or off-the-shelf systems. - Maintain
A strategy used for systems with high technical and low business values. Instead of modernization, these systems should be maintained. - Evolve
A strategy used for high-quality and high-business-value systems. It involves actively maintaining the system, introducing new features and products, and integrating it with other systems. - Re-engineer
A strategy for systems with high business value and low technical quality. This strategy implies preserving business value while re-engineering the system and managing technical debt. - Migrate
A strategy used for systems with high business value when the company decides to innovate with new technology. In this case, a legacy software migration to new technologies is performed.
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Legacy Modernization - More Strategies
Here are some other modernization strategies that can be used in combination with the aforementioned strategies and as standalone methods:
Chicken Little
Chicken Little involves a slow legacy system migration by small incremental steps. Each step implies a small resource allocation and produces a small result. It also allows for the separate step - cut-over - a process of switching from the legacy system to the target system, where sites, users, and data are iteratively cut over from the legacy system to the target system, site by site, user by user, etc. This strategy was proposed in 1993.
Renaissance
The RENAISSANCE method is a two-stage process for legacy software modernization. In the first stage, a stable basis is established with system assessment and evaluation of need and urgency. Stage 2 involves implementing the new system's planned transformation and continuous improvement.
Butterfly
The Butterfly method is based on the assumption that data is the most essential part of the system. The semantics or schema are also considered very important. So, the Butterfly method separates the target system modernization from data migration. In this methodology, the legacy data store becomes read-only when the legacy data migration begins. The Chrysaliser and Data-Access-Allocator (DAA) handle all the manipulations with data. Chrysaliser transfers data to the target system. The DAA stores the results of manipulations on legacy data in a TempStore (an auxiliary datastore). You can read more about this method here.
The Butterfly method uses a getaway-free approach, which doesn’t rely on a centralized getaway to manage data transfers.
Middleware and wrapping technology
The middleware and wrapping technology approach is best described by the Wells Fargo example. Wells Fargo offered customers online banking services, including transferring funds, viewing credit card charges and payments, downloading transaction files, etc. The system had 100,000 customers and 200,000 business object operations per day. The company left the legacy system untouched while adding CORBA middleware to create a three-tiered system using wrapping technology. So, a wrapping method implies “surrounding the legacy system with a software layer that hides the unwanted complexity of the old system and exports a modern interface.”
CORBA is now considered an outdated technology. However, wrapping is still used nowadays for legacy software modernization, for example, by packaging legacy services to make them usable by customers and businesses over the web via RESTful APIs.
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Service-oriented architecture (SOA)
The service-oriented architecture (SOA) approach segments a legacy system into services that contain both the code and the data to perform a function independently. It is about designing the system as a collection of services that can be easily reused and integrated into different systems. This approach allows the reuse of legacy functionalities within modern architectures without significantly changing the legacy system.
Reverse engineering
The reverse engineering approach implies first analyzing the source code to extract legacy requirements and then implementing the legacy requirements using the new technologies to generate the latest source code.
Low-code: The New Strategy for Legacy Modernization
Modernizing legacy systems with low code is a relatively new practice. It goes in line with Gartner’s continuous modernization framework.
The main points of this framework are:
- The Big Bang and rip-and-replace approaches to legacy application modernization are not sustainable.
- Continuous modernization minimizes the risks and costs of legacy system modernization. The main idea of continuous modernization is to find and remove obstacles to digital business from legacy applications. These obstacles are defined as friction points or points that prevent the system from fully supporting the business function.
- Continuous modernization enables composability. Composability is a design approach that separates essential elements into building blocks. Some blocks are considered acceptable and do not need modernization, while others are marked as having issues.
- For blocks that need modernization, Gartner offers encapsulating, reusing, or extending the current system. This can be done by implementing an API to reuse data and functions and building a web GUI. Another option is to replace a component with a more appropriate technology, for example, a SaaS or BaaS service, and then integrate it via an API.
Low-code development fits perfectly within Gartner’s continuous modernization framework. It allows you to build core or separate software functions and connect them via an API. Low-code platforms also allow innovation to move into the cloud while the main business functions are preserved as systems of records.
- The Big Bang and rip-and-replace approaches to legacy application modernization are not sustainable.
- Continuous modernization minimizes the risks and costs of legacy system modernization. The main idea of continuous modernization is to find and remove obstacles to digital business from legacy applications. These obstacles are defined as friction points or points that prevent the system from fully supporting the business function.
- Continuous modernization enables composability. Composability is a design approach that separates essential elements into building blocks. Some blocks are considered acceptable and do not need modernization, while others are marked as having issues.
- For blocks that need modernization, Gartner offers encapsulating, reusing, or extending the current system. This can be done by implementing an API to reuse data and functions and building a web GUI. Another option is to replace a component with a more appropriate technology, for example, a SaaS or BaaS service, and then integrate it via an API.
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Challenges of Legacy Modernization
Currently, the types of BaaS include cloud backend as a service, self-hosted BaaS, open-source Baas, and low-code platforms.
Here are a few of the most popular BaaS:
1. Finishing legacy modernization
Legacy modernization projects take significant time and resources, so it is not surprising that finishing them is often a challenge. You run out of time and resources, such as budget, experts, and knowledge. Some developers experience continuous modernization challenges, where legacy modernization projects run for 3 years and are still incomplete after 5 years.
2. Data migration issues
Most developers agree that data migration cannot be done perfectly, which creates challenges for legacy modernization. Sometimes, the issue is that the legacy system doesn’t support modern databases; for example, the database is not schema-less.
3. Complex system architecture
Poorly designed or monolithic architecture is another challenge of legacy system modernization. Architecture affects how the data is stored and migrated and how testing is conducted. 56.4% of developers claim it is difficult to test a legacy system that is being modernized due to inability to extract all use cases following a poorly designed architecture.
4. Lack of knowledge
60.7% of developers indicate a lack of knowledge as a challenge in legacy software modernization services. Knowledge of databases, operating systems, middleware, and architecture is required. Additionally, knowledge of transforming business functions from one system to another is needed. Some developers mention that documentation plays a crucial role in modernization efforts. If documentation is lacking, there is a significant risk to migrate. A reverse engineering technique is often used to document the old system and understand the requirements for the new system.
5. Difficulty to extract and prioritize business logic
Business logic in legacy systems needs to be extracted before modernization. Due to the lack of knowledge, this extraction is sometimes challenging to perform. Sometimes, building diagrams and maps helps, but it is only possible if you know what the system does at each step.
6. Resistance from the company
Business logic in legacy systems needs to be extracted before modernization. Due to the lack of knowledge, this extraction is sometimes challenging to perform. Sometimes, building diagrams and maps helps, but it is only possible if you know what the system does at each step.
7. Other challenges
Other challenges include the so-called soft factors, which are not technical and are not connected to a lack of technical knowledge. These are people, communication, and business values. These factors range from stakeholders not prioritizing legacy modernization and not allocating budgets as they prefer short-term Return on Investment.
Legacy Modernization Paradoxes
Legacy systems are brimming with paradoxes. Here are just a few of them from the studies:
Legacy systems are not obsolete systems
Surprisingly, legacy systems are not always perceived as needing modernization. Most developers think legacy systems are not old and obsolete but rather core systems that sustain the business. These systems have been running for years, are reliable, and are well-tested. So, the main factor determining whether the system is legacy is how well it fits within the business requirements, not its age.
Legacy systems are cash cows
Among developers, legacy systems are considered the “backbone” of the business that generates revenue. Therefore, they are critical systems to maintain. Legacy systems are perceived as profitable and of great business value.
If it isn’t broken, don’t fix it
Some developers consider modernization unnecessary for legacy systems, citing factors such as “it has been working,” “they have been working—why fix it?” by a developer with 17 years of experience with legacy systems, and “we didn’t fix it last year, and survived. Why should this year be different?” by a chief technical officer of a software development company.
How ondeva low-code platform can facilitate legacy modernization
In conclusion, we provided a comprehensive overview of legacy systems and modernization strategies. Legacy systems have a critical role within businesses due to their proven reliability and the significant revenue they generate despite being built on older technologies that may not align with current technological goals.
We introduced the concept of continuous modernization as a sustainable approach, facilitated by low-code platforms, to incrementally update systems without the need for a complete rebuild.
ondeva Low-Code is an easy-to-use app development platform that lets you build apps with little coding. You can move data from legacy systems, set up processes, and transfer everything to ondeva. Once your data is on ondeva, you can use many tools.
If you want to improve users' experience and make your apps look better, ondeva is a great choice. It lets you quickly create new web or mobile interfaces for your legacy systems. With simple drag-and-drop actions, you can add pre-made design elements and generate a theme with the help of AI.
ondeva aims to improve business operations and eliminate problems caused by insufficient digital transformation. If you're looking for a simple way to update your legacy system, create a free account with ondeva today.
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FAQ
Legacy Modernization is the continuous process of updating Legacy Systems to meet technological advancements and business requirements, simplify the IT environment, reduce costs, enhance data consistency, and setup collaboration across different platforms, to increase flexibility.
An example of legacy modernization includes migrating an old, monolithic application to a cloud-based architecture, which improves scalability and performance without altering the core business logic.
Legacy modernization approaches can be varied. You can rehost the application to a cloud environment for better scalability; refactor the code to enhance maintainability and performance without altering its functionality; replatform to leverage new platform features with minimal code changes; replace it entirely with a new solution and many more other approaches.
Legacy systems are usually modernized for several reasons: to maintain agility and adapt to changing business needs. Often built on outdated programming languages, legacy systems lack the flexibility required for today's market. Maintenance of legacy systems can also be costly. A major concern is the risk of failure, associated with the lack of knowledgeable experts available to support legacy systems.
