BLOGAnnounced at MongoDB.local NYC 2024: A recap of all announcements and updates — Learn more >

Application Modernization Ultimate Guide

Discover what application modernization is, why it's important, how MongoDB can help and how to get started.

Legacy applications can be the backbone of organizations. They provide value to customers and can bring significant revenue to companies. Unfortunately, legacy applications also bring with them their own web of challenges: complex, rigid systems that are difficult and daunting to update, expensive infrastructure that is costly to maintain, and an unwieldy deployment process that can lead to infrequent releases.

Modernizing these legacy applications is vital to speed up innovation and bring new value to your customers, and ultimately is critical to the long-term success of your business. But should organizations take on the cost and effort of modernizing their legacy applications? If so, how?

In this article, you'll discover the answers to the following questions:

What is Application Modernization?

Application modernization (also known as legacy modernization, software modernization, digital transformation, and cloud transformation) is the process of updating legacy applications to use modern programming languages, frameworks, infrastructure, services, automation, and cloud infrastructure. The following are examples of modernizing applications:

  • Refactoring a monolithic application into microservices

  • Migrating an application from on-premises to the public cloud

  • Replacing infrequent, manual deployments with frequent, automated deployments

  • Distributing clusters across multi-cloud environments

  • Replacing a relational database with a modern database, such as MongoDB

Why is Application Modernization Important?

Application modernization is vital for companies with existing legacy applications who want to innovate quickly and rapidly to bring new value to their customers. Developers reported that maintaining legacy systems and technical debt is the top hindrance to developer productivity at their companies, according to a survey from Stripe and Harris Poll.

Developers and operations engineers who work on legacy applications face many challenges:

*Updating huge, monolithic applications is difficult due to application complexity.

  • Scaling a highly used piece of an application (rather than the entire application) can be problematic, if not impossible.

  • Managing legacy systems and legacy applications on-premises can be expensive and time-consuming.

  • Infrequent, manual deployments tend to be large and, therefore, risky.

  • Relational databases have rigid, complex schemas that can slow development time and new feature delivery, reduce operational efficiency, delay business processes, and require application downtime in order to be updated.

These issues can lead to a product being late to market, among other missed opportunities.

What are Application Modernization Patterns?

Several application modernization patterns exist. Typically, patterns that require more investment reap higher rewards for most organizations.

  • Rehost or redeploy. When you rehost or redeploy your application, you typically "lift and shift" the application from an on-premises deployment to public cloud, private cloud, hybrid cloud, or multi-cloud environments.

  • Replatform. When you replatform the application, you modernize an aspect or aspects of the application's platform, like the underlying database. Replatforming typically requires some modifications to the code base.

  • Refactor or rearchitect. When you refactor, you update the code base to make improvements to the code itself without changing the application's functionality. Rearchitecting the application could require updating the code base in order to take advantage of modern architectures, such as containers or microservices.

  • Replace. When you replace the application, you start from scratch with an entirely new code base. One option is to replace the legacy application feature for feature. Another option is to reimagine the application completely, deciding what features to drop and what new features to implement.

What are the Key Technologies for Application Modernization?

Every application modernization project will be unique. However, a few key technologies frequently appear in the modernization journey.


Teams may choose to containerize their applications, so the applications can be packaged and deployed consistently, regardless of the environment where they are deployed (locally, on-premises, or in the cloud). This consistency can be helpful throughout the entire software development life cycle, from development to testing to deployment to support.


Teams may choose to break a huge, monolithic application into several smaller microservices. A microservices architecture provides several benefits including faster time to market, modularity, flexibility, scalability, resiliency, organizational alignment, and reductions in cost.

Serverless Functions

Teams may choose to package application functionality into discrete functions that are fully managed in the cloud. Cloud providers, backend-as-a-service (BaaS) providers, and other development platforms such as Vercel handle running and scaling serverless functions, so developers can focus on writing the business logic and calling the functions. MongoDB is commonly used with serverless functions and offers a serverless database option to scale database resources alongside application usage.

The Cloud

Teams may choose to move from managing their own infrastructure and tech stack to using infrastructure and services in a public cloud, private cloud, or hybrid cloud. Teams may also choose to use a multi-cloud strategy to avoid cloud vendor lock-in.


Teams may choose to move from rigid relational databases to more flexible, modern databases, such as the MongoDB Atlas developer data platform. MongoDB databases have flexible schemas that allow for both structured and unstructured data. MongoDB offers self-managed instances or fully managed instances on multiple cloud providers through MongoDB Atlas.

CI/CD Automation

Teams may choose to move from infrequent, manual deployments to frequent, automated deployments by implementing CI/CD (continuous integration/continuous delivery or continuous deployment) pipeline automation. Infrastructure-as-code (IaC) tools can be used to automate and manage the deployment of cloud resources. Atlas has an Admin API that can be used for scripting and resource providers for HashiCorp Terraform and AWS CloudFormation to quickly build, update, and manage MongoDB databases in the cloud.

How Do You Perform Legacy Application Modernization?

Application modernization is a two-phased process: initial assessment and execution.

In the initial assessment phase, the team works together to assess the entire application portfolio and understand the application's details. As part of the assessment, applications are rated on factors such as technical implementation, interconnectedness with other applications and systems, anticipated return on investment, and drivers for change. If the application receives a high rating, the team performs a deeper evaluation to estimate the application modernization efforts. The team iterates in order to assess all of the applications. Then the team determines prioritization and creates an application modernization roadmap.

Once the application assessment phase is complete, the team will begin the execution phase. In this phase, they will follow the application modernization roadmap. They will typically do the following for each application that was selected for the modernization process:

  • Design and architect the application modernization.

  • Implement the application modernization, which could involve rehosting, redeploying, replatforming, refactoring, rearchitecting, or replacing the application.

  • Validate and test the application outputs.

  • Deploy the modernized application.

Note that the steps in the execution phase can be completed in a waterfall model or iteratively. In the waterfall model, each step is completed for the entire application before going to the next. In the incremental model, each step in the phase is completed for a small piece of the application. Then the steps are repeated again for another small piece of the application.

A rectangle represents the Assessment Phase. Inside of that rectangle are smaller rectangles representing steps in the Assessment Phase: Assess Application Portfolio and Understand Application Detail. An arrow points from the Assess step to the Understand step. The assessment phase has an arrow pointing to another large rectangle representing the Execution Phase. Inside of that rectangle are smaller rectangles representing steps in the Execution Phase: Design Application Modernization, Implement Application Modernization, Validate Application Outputs, and Deploy Modernization Application. The steps are arranged from left to right with arrows between pointing from the step on the left to the step on the right.

The phases of application modernization.

Why Do Enterprises Need Application Modernization?

Enterprises and businesses of all sizes can see numerous benefits from application modernization:

  • Increased developer productivity

  • Reduced infrastructure costs

  • Better application performance

  • Faster time to market

  • More frequent releases

  • Increased customer satisfaction and retention

  • Future-proof business needs

  • Greater business agility

  • Digital transformation/cloud transformation

Businesses that are not modernizing their applications may run the risk of being unable to innovate quickly and achieve business goals.

How Does Application Modernization Work with MongoDB Atlas?

One common type of application modernization involving MongoDB is moving from a legacy, relational database to MongoDB Atlas. The MongoDB Atlas developer data platform is centered around a fully managed MongoDB database, available in over 95 regions on AWS, Google Cloud, and Microsoft Azure. Atlas is an easy-to-use and cost-effective modern service with capabilities such as auto-scaling, serverless instances, and multi-cloud data distribution. These capabilities allow development teams to focus on their applications without the hassle of managing databases themselves.

When you modernize an application from a relational database to the MongoDB Atlas developer data platform, you will want to do more than just "lift and shift" your database. Migrating the data from a relational database's table to a MongoDB collection would certainly work, but the application would likely not reap all of the benefits of modernization. Instead, the team should identify how the data will be accessed in the application and create a new, transformed data model. For a detailed comparison of "lift and shift" database migration versus a modernized and transformed database, check out the "Why the MongoDB Intelligent Operational Data Platform?" section of Legacy Modernization.

Development teams and their key stakeholders have several options for moving data from a relational database to MongoDB:

  • Write a script that transforms the original application data into JSON and then import that data into MongoDB using the mongoimport tool.

  • Use an Extract Transform Load (ETL) tool to migrate the data from a relational database to MongoDB. ETL Vendors such as Informatica and Pentaho have created MongoDB connectors specifically for this task.

  • Migrate the data incrementally so that both the legacy database and modernized database run in parallel.

Many development teams have successfully completed the migration process on their own. When development teams desire external expertise on how to complete the migration, they can work with MongoDB's professional services team to build an Application Modernization Factory. Throughout the process of building the factory, the MongoDB team provides consulting, program governance, and expertise to ensure the migration is successful.

What Does a Developer Data Platform Do?

MongoDB Atlas, the industry’s leading developer data platform, simplifies development for a wide variety of use cases, scales globally and securely, and optimizes cost-for-performance as your data needs evolve over time. That means you can run anywhere in the world and build modern applications faster to accelerate your go-to-market timelines and gain competitive advantage.

MongoDB Atlas is built on the document model, which means it's flexible and maps to how developers think and code. Developers enjoy a unified interface to work with any data generated by modern applications, with fully integrated text search, eliminating the need for a separate search engine. It provides organizations with a flexible local datastore with seamless edge-to-cloud sync. It offers in-place, real-time analytics with workload isolation and native data visualization. You can run federated queries across your operational and transactional databases and cloud object storage. And it's built upon the most resilient, scalable, and secure platform available, with turnkey global data distribution for data sovereignty and industry-leading data privacy controls. With Atlas, you can deploy across clouds in 95+ regions.

MongoDB Atlas solves the biggest challenges for companies by eliminating the technical debt from legacy systems in the data infrastructure, helping them drive innovation, reduce risk and operational costs, modernize their underlying infrastructure, and achieve true digital transformation.

Should You Modernize Your Database to MongoDB?

Modernizing your database to the MongoDB Atlas developer data platform can lead to a variety of benefits including:

  • Improve application performance

  • Reduce costs

  • Increase developer productivity

  • Strengthen resilience

  • Increase scalability

  • Enable global data distribution

  • Avoid platform lock-in

  • Accelerate innovation

  • Increase business agility

  • Enhance customer experience

But how do you know if the effort required with modernizing your database is actually worth it?

The MongoDB Modernization The MongoDB Modernization Scorecard allows you to identify which of your existing systems are good candidates for being modernized to MongoDB. Download the MongoDB Application Modernization Guide to get a copy of the Application Modernization Scorecard and determine whether a modernization effort makes sense for your business needs.


Application modernization leads to a variety of business benefits including increased developer productivity, reduced infrastructure costs, more frequent releases, and faster time to market. Application modernization encompasses a variety of ways to modernize your application including rehosting, redeploying, replatforming, refactoring, rearchitecting, or replacing the application.

If you want to modernize the database in your application, the MongoDB Atlas developer data platform is a great place to start. Download the MongoDB Application Modernization Guide to get a copy of the Application Modernization Scorecard, see an example schema that was migrated from a relational database, and read the RDBMS to MongoDB Migration Guide. If you'd like professional assistance in your database modernization, check out the Application Modernization Factory.

Your company’s competitive advantage lies in its ability to unleash the power of software and data to build richer digital experiences. MongoDB makes it incredibly easy to go from an idea to an application serving users all over the world — whether it’s a new application or optimizing an old one. Increase your development team's ability to build the next big thing and get your ideas to market faster by modernizing your database with MongoDB Atlas.


What does application modernization mean?

Application modernization—also known as legacy modernization and software modernization—is the process of updating on premises environments, legacy systems and monolithic applications to use modern technologies, such as programming languages, frameworks, infrastructure, services, and automation.

How do you modernize a legacy application?

Teams modernize an existing application by taking the following steps:

  • Designing and architecting the application modernization.

  • Implementing the application modernization, which could involve rehosting, redeploying, replatforming, refactoring, rearchitecting, or replacing the existing system or application.

  • Validating and testing the modernized application.

  • Deploying the modernized application.

What are the advantages of modernization?

Application modernization has a variety of advantages, including increased developer productivity, reduced infrastructure costs, better application performance and customer experience, faster time to market, more frequent releases, and increased business agility.

What are application modernization strategies?

Teams can modernize an application by rehosting, redeploying, replatforming, refactoring, rearchitecting, or replacing it.