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Application Modernization and its Challenges | Quick Guide

Navdeep Singh Gill | 30 May 2023

What is Application Modernization? 

Application Modernisation refers to the change specifically modernising the features, platform, internal and external infrastructure or anything related to the software or application. This process updates or rebuilds the present architecture to be effective in the upcoming or present modern environments. Opening doors to never seen before benefits and growth. 

As good as it sounds, severe complex issues are to be addressed and resolved to achieve application modernisation. Issues like spaghetti code, inflexible architecture, inability to scale are faced while undergoing this process. Let us get an in-depth review of this process.

Legacy applications and infrastructure are becoming unsustainable and non-cost-effective in the cloud-native world. Taken From Article, Key Aspects of Infrastructure Modernization

What is a Legacy Application?

Legacy typically refers to an application's monolithic architecture. Single tier application where all the pieces are built on one platform, usually with one language. This does not mean that legacy applications are small; they can be big as an elephant, making it difficult to scale as per the requirements. One single bug can affect the working of an entire application. 

Legacy systems are outdated technologies but are critical in day to day operations. Rolling out a minor new feature or version can be as big as rolling out the whole application again. Legacy applications are also referred to as Monolithic applications, which consist of a single codebase where all components such as authorisation, business logic, databases, messaging service, etc., are combined on a single platform. These systems have become fundamental to the working of an application and the organisation; thus, replacing them is not always easy. So what is the need for modernisation? Why replace or shift to something new and different

Modernizing Legacy Applications for a Variety of Reasons

Modernizing legacy applications may be beneficial for several reasons, including:

The Cost and Complexity of Maintaining Legacy Software

Much of a company's IT budget goes toward maintaining legacy systems. In addition to being complex, maintaining outdated software is highly costly. As a result, these systems no longer meet the business needs or perform certain functions they were built to perform. Technology and processes have advanced rapidly since the development of these archaic systems, making it difficult to maintain them.

Furthermore, finding individuals with relevant skill sets with experience in creating and maintaining outdated systems becomes increasingly more work. Consequently, many companies are forced to outsource dedicated IT support and pay exorbitant salaries to personnel who could help maintain the legacy software. Instead of spending vast amounts on maintaining legacy software, businesses should consider modernizing it to reduce costs and complexity.

Businesses should consider modernizing legacy applications to reduce maintenance costs and complexity.

Enhance Performance With Modern Technology

By modernizing legacy software, you can identify opportunities and threats associated with the existing technology. Businesses can combine what is still relevant from their existing software and build something new using application modernization services instead of replacing their old system and building a new one from scratch. Your legacy system can be improved by enhancing it with modern technology and eliminating inefficiencies and bottlenecks.

Companies can address productivity issues by automating and integrating IT and business solutions. By increasing productivity, businesses can perform operations with less manual labor, lower costs, and fewer downtimes.

Modernize Legacy Applications to Prevent Security Threats

Security threats are more likely to affect legacy systems. You will no longer get security patches whenever the developer stops supporting or updating the software. A significant challenge has also become disaster recovery and backup. Using old SSL and Java exploits, your network will be more vulnerable to malicious hackers.

Therefore, your company and its users might be at risk of data theft or a hack of the entire system. The modernization of legacy software allows businesses to enhance functionality and improve security. Cybercrimes can be identified and prevented with newer technology applications built with advanced security measures. You can also reduce the risks of cybersecurity threats by updating your security patches regularly and using cutting-edge SSL encryption.

What are the Technologies for Modernizing Applications?

To improve legacy applications' performance, security, and functionality, modernization involves updating them with more modern technologies. Application modernization commonly uses the following technologies:

Cloud Computing

As part of application modernization, applications are always re-platformed or rehosted on the cloud. Organizations can use public, private, hybrid, and multi-cloud options to use cloud computing's scalability, agility, and lower cost.  

Microservices Architecture

Monolithic applications can be developed, deployed, and scaled independently by breaking them into smaller, independent components. This approach's advantages for modern applications are scalability, reliability, and speed.


Cloud and on-premises applications can be managed and scaled more easily with containers because they package and deploy multiple applications and their dependencies into a single unit.

Serverless Computing

An application runs on a serverless cloud model, where the provider manages the infrastructure and automatically allocates resources as needed. Running applications using this approach can reduce operational overhead and costs.

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What is the strategy for Modernizing Legacy Applications?

It is important to note that the appropriate strategy will vary depending on the specific needs and constraints of the organization and the application. It's good to assess the current state, goals, and constraints to decide on the best strategy.


Rehosting a legacy application means moving it to a more modern infrastructure like a public cloud platform. It is also known as lift-and-shift. The benefits of this strategy include cost savings, security, and increased reliability by shifting your physical servers and virtual machines to the cloud. Upon completion of the shift, the cloud provider manages the current hardware and operating system. Managing workloads or applications and operating them remain the same.


In refactoring, a code is rewritten, restructured, or repackaged. As part of this approach, the underlying code of a legacy application is revised to improve its performance, cost, and reliability in a new environment. Your current application can continue to run as-is with a few minor changes in code and configuration and be connected to new infrastructure services such as containers, databases, and identity management systems.  


An application can be redesigned or rewritten modularly using this strategy. A cloud platform offers better scalability and reliability by optimizing or extending an existing application's codebase. Changing the app code is the most time-consuming step when migrating to the cloud. Using microservices to implement a monolithic application on the cloud would be an example of rearchitecting.  


Incorporating cloud PaaS and SaaS services into an existing application involves rebuilding the application. Redesigning the application for the cloud means re-architecting it. You can decompose the original application and deploy it on a cloud platform by redesigning the code and breaking it into smaller chunks.  


In this case, an existing application is discarded and replaced with a cloud-based application delivered as a service (SaaS). In this strategy, a service provider manages the underlying infrastructure, middleware, app software, and app data, ensuring the app's availability and security. 

Why is Application Modernization needed?

As we know, two of the major setbacks of a monolithic system/application is that it is challenging to upgrade, challenging as well as expensive to scale. Here are some other major issues faced in a monolithic architecture are -

  • Vulnerable security
  • Incompatible
  • Not very cost-effective
  • Customer Experience
  • Technical specifications

Vulnerable security

The inevitable old application does not always receive upgrades to fulfil today's security requirements. This leads to loose ends and compromised security on all layers.


Applications built on monolith architecture are usually standalone and not open to integrations. This limits the use case and flexibility. Today being compatible with other applications in the market can directly lead to growth in business.

Not very cost-effective

One must think that a monolithic architecture is built as a single-tier application, making it less expensive to scale, but this becomes less true over time. Supports and updates for older systems are usually expensive and can even result in conflicts because of one codebase.

Customer Experience

All of the above-mentioned points directly affect the customer experience. Not receiving timely updates is one of the major ones. One happy customer can lead other customers in the bucket but this can also happen oppositely.

Technical specifications

The digital and tech industry is growing every hour, taking leaps a day, and legacy applications could even date back to the 2000s. Not being compatible with the latest hardware makes the application obsolete.

Legacy applications and infrastructure are becoming unsustainable and non-cost-effective in the cloud-native world. Click to explore about our, Stateful and Stateless Applications

How to get started with Application Modernization? 

An organisation can take plenty of approaches to change the scenario and modernise the application — varying from combining platforms, exposing APIs, complete migration, etc. Here are some of the known techniques which have been proved with user stories of big companies, including fortune 500 

From monolith to microservices 

Monolithic architecture can be challenging to deal with. Segregating components from a single extensive framework can open the application to more resilience, flexibility and scalability. The microservice architecture breaks down the application into multiple small services. Any issue or fault in a microservice-based application affects only a particular service instead of the whole application. This results in better and quick debugging

Rolling out updates and new features is easy compared to a monolithic application. Splitting the codebase into loosely coupled dedicated services and identifying the logical components of the application with their dependencies is a good way to get started with this journey of the monolith to micro.

A strategy known as "strangler pattern" takes down the application bit by bit, taking out the most valuable services or components first. Eventually, there is nothing left with the monolithic, leading from easy to complicated components.

Cloud Migration 

Cloud Migration is one of the most demanded and adopted strategies in the past few years and it's said that cloud is going to have a never seen before workload. Organisations and companies undergo cloud migration to achieve the digital transformation — shifting all the workload from legacy, on-premise business operations into the cloud.

Clients can choose from different types of cloud-like Hybrid or multi-cloud depending upon the requirements and business operations. One of the most commonly used Cloud migration strategies is lift and shift. It is relatively quicker than the other approaches. It includes taking an exact copy of the application with all the dependencies like databases and OS over to the cloud without any changes to the application's architecture. Reduced IT costs, security competence, accelerated growth, and leveraging new technology benefit from shifting to a cloud platform.

Exposing APIs 

This approach is more about integration rather than migration. As known, old legacy applications contain flaws such as not being mobile-ready, less platform support and affecting business processes. By exposing APIs, access is created to your business logic using an Interface (API). This even transforms a feature more as a product in itself. Rewriting or changing the existing application code to function for different platforms can cost much more than just exposing APIs.

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Challenges of Application Modernization and their Solutions 

Change is not always easy to handle, and especially shifting from the present architecture to the one which promises scalability, efficiency, and many more benefits could be daunting. It's also known that several organisations that started the journey of application modernisation were not able to complete and failed while trying. Several impediments are faced while undergoing the application modernisation process. Let us discuss some of them: 

Skills shortage and IT skill gap

Mainframe architecture and its components are difficult to work with. Understanding these technologies is tough but understanding their interdependence is far more complex. Developers are no longer in touch with the application, and it's working. It may require acquiring new staff for the newly migrated application. This leads to added costs and complexity. Other relative issues are patched source code missing or irrelevant documentation. 

Solution: This will require recruiting from unconventional labour pools, training employees, collaborating with educational institutions to increase graduate employability, and competing for top talent globally.

Legacy ecosystem

An application ecosystem is built out of various technologies, bringing and making them work together. There could be different protocols, programming languages, databases, file formats etc, coming together on a single application. All these build the ecosystem of the application and changing it all in one go could lead to severe issues, ultimately affecting business.

Solution: In such circumstances, a chunking strategy must be used. The organisation needs to prioritise the most important ones first and then move on to the remainder. Also, organizations need to prepare specific tools and build the application to accommodate the old methods so that there is no disruption to the current business flow in the meantime. 

Data Migration 

The amount of data receding in a legacy application's backend would be loads. The number of business transactions could be in terabytes or petabytes. Hence, leading to a challenge with the migration of data from legacy to modernised application. It could even lead to data loss, and some types of data, if lost, can cause blunders. To tackle these difficulties, businesses must adopt an application modernisation strategy that supports three critical organisational success criteria: simplicity, productivity, and scale.

Solution: There are solutions on the market and specific ETL plugins that assist in moving data effortlessly to account for variances in encoding. Suppose the legacy programme is required to deal with files containing data in non-contemporary encodings. In that case, we must have the proper infrastructure in place. VSAM files might be transferred to SQL or NoSQL databases in the old system.

What are the Best Practices for Modernizing Applications?

There are several strategies and best practices that organizations can use to modernize their applications. The following are some best practices for application modernization:

Embrace Microservices

Your application can be made more scalable and agile by adopting a microservices approach. An environment that uses microservices separates each process into a separate service with its logic and database. As a result, services are independent and scalable, making updating or changing them more accessible.

Identify Applications that need to be Modernized

To modernize all applications, it is essential to identify them. It is important to sort these according to their priorities and requirements once selected. We must then understand the risks associated with modernizing each application and develop an approach for minimizing those risks. The value of the modernized app should be weighed against the time and costs associated with its modernization. It is viable to proceed with modernization if it is expected to improve agility, scalability, reliability, and performance.

Take Advantage of Cloud Computing

Modernizing apps means something other than automatically moving them to the cloud. It is essential to consider how much data will be involved, what kind of workflows will be required, and how devices and the cloud will communicate.

Keep Track of Performance Metrics

To track the performance of applications at the code level, it is essential to design performance metrics. Monitoring includes all aspects of the infrastructure, including the cloud, databases, and networks. Identifying problems before they arise and improving areas allows you to prevent them from occurring. 

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Beyond a doubt, it is evident that organizations need faster operations faster services in today's dynamic landscape. In contrast, legacy products tend to be more costly, demanding more grind. Modernisation offers new and different opportunities to organisations, leveraging new IT architecture. The best part is that it can be done according to and within the parameters set by the organisation. Thus, organisations can achieve the digital transformation they desire by modernising their legacy application by considering the approaches mentioned above and challenges.