Application Modernization Checklist

Application Modernization

Carefully strategize your application modernization when going cloud native on AWS, with a checklist of considerations and best practices.

Modernizing legacy applications enables your business to move fast! By modernizing your legacy applications to leverage cutting-edge cloud infrastructure, you can improve performance, reduce costs, make quicker business decisions, and increase reliability, availability, and flexibility. This application modernization journey can be a significant effort, but you have many choices in how you plan for it. With good preparation and solid decision-making, you can modernize your application and begin reaping the benefits.

The objectives of app modernization

A successful application modernization project should result in several benefits, and it will be up to you to pursue the benefits that are most important or meaningful for your application. 

As a starting point, consider the example of running a custom, on-prem application hosted on physical servers in your data center. This scenario could encounter several difficulties:

  • application downtime due to maintenance
  • server patching and security compliance
  • server upgrade costs
  • licensing costs for third-party database engines
  • overprovisioned infrastructure to meet peak demand due to limited scalability options
  • hiring new team members with the right list of legacy skills

Each of these issues can be addressed through application modernization.

Rehosting from physical servers to EC2 instances would improve scalability while removing the need to overprovision. Replatforming by moving to containers would further enable efficient usage of infrastructure while making your application portable, scalable, and reliable. And using cloud-managed services as part of your legacy modernization solves problems with patching, security compliance, server upgrades, reliability, and more. The final, and many times most challenging, approach is refactoring or rearchitecting your application. This takes more time, energy, and money but results in extreme improvements in the areas of performance, extensibility, and future-proofing, alongside all of the other benefits mentioned above.

What a modern app looks like

A modernized application should have the following key traits:

Be Cloud Native: modern apps should utilize and integrate with cloud services. Only by living in the cloud can your application leverage the benefits of cloud computing, such as extreme scalability, cost efficiency, and agility.

Follow a Modern Architecture: for example, use a microservices architecture to decouple monolithic functionality into smaller, discrete modules that can be updated and deployed independently for greater flexibility and improved performance.

Use Modern Components: for example, leverage containers to package, deploy, and operate your application to achieve scalability, portability, and operational efficiency.

Incorporate Modern Development: use modern frameworks to save time writing new code by using established patterns and templates, and improve developer efficiency through proven development processes. Use modern languages that can speed up coding time, open the door to new development techniques, and attract the brightest talent to your team. 

Employ Orchestration and Automation: coordinate and manage automations to create cohesive, easily repeatable, rules-based workflows. Orchestration is commonly used in container deployment automation, but can also be leveraged for application deployment automation, such as the workflow in a CI/CD pipeline. This saves developer time by automating repetitive tasks and increases app quality through automated testing and validation.

The app modernization checklist

  • Preparation
  • Application Assessment
  • Modernization Roadmap
  • Containerization
  • Refactoring
  • Pipeline Development


Preparation is arguably the most important step in your application modernization journey. Defining the business outcomes required for success and iterating through the timeline, milestones, priorities, and other drivers will all be key elements of successful preparation. Successful and detailed preparation enables you to set realistic goals and milestones with users and stakeholders.

The preparation phase of your application modernization checklist should include identifying, documenting, and prioritizing the following:

  • Legacy application pain points and functionality gaps
  • Convert this list into technical objectives and milestones for modernization
  • Desired and required business outcomes
  • Convert this list into the success criteria for overall application modernization
  • This list might include things like lower costs, better scaling, more reliable deployment, greater frequency of deployments, and the list can go on. Identifying these early will help drive the modernization effort.
  • All related software, databases, integrations, and dependencies that could be impacted
  • Convert this list into prioritized prerequisites for discovery and app assessment
  • RACI for stakeholders involved in deciding which application modernization approach(es) will be employed

Application Assessment

An application assessment will require input from your technology teams and business teams who support and maintain the app, users who rely on the app, and stakeholders who will play a role in the app modernization. Collaborate with your technology experts, power users, and cross-business teams to define where each part of the checklist below belongs on the continuum from critical to not applicable. Special attention should be given to include secondary or even tertiary stakeholders. For example, even if the database team doesn’t support the legacy application directly, they could be impacted by the modernization effort and should be consulted or informed. 

Customize the checklist to fit your needs since it is likely your environment includes unique circumstances that will need special handling.

The app assessment phase of your application modernization checklist should include identifying and documenting the following:

  • Full tech stack required to run the application
  • Frameworks, languages, libraries, and dependencies used by the application
  • Databases, application servers, middleware, legacy hardware
  • Data flows, architecture diagrams, business workflows
  • All shared services, such as logging, backup, monitoring, and directory services
  • Applications or services that share a data source with the application
  • Users of the core application and consumers of downstream services 
  • Inbound and outbound interfaces, along with the interface types and protocols
  • Strategies and technologies used for caching, clustering, queuing, state management, scalability, testing, deployment
  • Security and audit requirements, source code control, change management standards, and other internal controls you will need to follow as you modernize

Modernization Roadmap

Once the application assessment is complete, you will have a rich data source for deciding the best modernization method and strategy for your application. And based on criticality and priority, you can decide to focus on the biggest pain points first or on the business outcomes you want to achieve first. 

The roadmap phase of your application modernization checklist should include identifying and documenting the following:

  • Method for modernization (containerization, refactoring, hybrid, any of the 7 Rs)
  • Choose relevant technologies, platforms, frameworks, languages, and logging
  • Project scope and objectives
  • Define explicit goals for what is included and what will be done
  • Risks along with plans for mitigation, acceptance, avoidance, etc.
  • Deliverables and milestones listed in phases with timelines
  • Resource requirements
  • People – coders, testers, user acceptance, project management, etc.
  • Time – driven by phases and timelines above
  • Budget – stakeholder approvals for making the investment


If you decide moving your app to containers should be part of your modernization strategy, you will have additional decisions to make. Containerization will require planning and good execution, but when done right, containers bring significant benefits in cost reduction, app portability, scalability, dependability through standardization, and efficient use of resources.

The containerization phase of your application modernization checklist should include making decisions in the following areas:

  • Container technology most appropriate for your environment
  • Container management system to be used for registries, orchestration, security, tools, and monitoring
  • Complementary technologies to include, such as Amazon EKSAWS FargateAWS App Mesh, and microservices architectures
  • Training and upskilling for existing team members for deployment and ongoing support
  • Roadmap for container deployment: exploration, pilot, limited rollout, expanded rollout, enterprise adoption


When it comes to options for application modernization, refactoring can be the best approach to take, but it can also be the most scary and resource intensive. Refactoring gives you the ability to rework and improve vast swaths of your application (if not the whole thing) and gives you laser-like precision in how your application gets modernized. Whether it’s decomposing a monolith into microservices or refactoring code to be more concise, refactoring can help you to meet your exact goals.

The refactoring phase of your application modernization checklist should include making decisions in the following areas:

  • Language(s) and framework(s) most appropriate for the components being refactored
  • When choosing the correct language or framework, keep in mind the staff that are required to maintain the component going forward.
  • Management tools needed to support new development, such as deployment framework, source code management, development environments, and static code analysis tools
  • Development architectures to guide implementation, such as the AWS Serverless Application Model, event-driven development, microservices architecture
  • Training and upskilling of existing team members for development, deployment, and ongoing support
  • Roadmap and priority list for which application components will be refactored, where the interlaced dependencies are, and how they will be coordinated for development and deployment
  • Detailed discovery of the component being refactored around the impact on data sources, integrations, logging, alerting, and the user base prior to starting work

Pipeline Development

A crucial piece of a modernized application is the implementation of a deployment pipeline. This orchestrated, standardized process will save time, increase productivity, improve quality, remove error-prone manual steps, enable automated testing, and deploy a stable, reliable version of the application to the right environments.

The pipeline phase of your application modernization checklist should include making decisions in the following areas:

  • Deployment workflow, including phase automation along with manual decision points
  • Integrate with prior decisions for source code management, development environments, and deployment frameworks
  • Environments for automated deployment such as DEV, QA, STG, PROD
  • Automated testing specific to each phase of the workflow
  • Aligned testing methodologies specific to each environment 
  • Multi-environment deployment practices
  • Roll-back and roll-back triggers for failed or less-than-desirable deployments

Tips for your app modernization

Application modernization comes with many benefits, and it is easy to focus on all the great things to look forward to. But, of course, there are pitfalls to watch out for. If done incorrectly, an application modernization journey can be delayed, derailed, expensive, or downright destructive.

Examples of pitfalls include misaligned business goals, taking shortcuts, not having everyone on board and the potential for high investment requirements, as mentioned above.

There are also best practices that can help achieve successful modernization:

Ensure readiness gets the attention it deserves: don’t take shortcuts during preparation and readiness. Give full time and attention to research, documentation, and decision-making during these early stages.

Modernize using a granular approach: build a component-based or functionality-based roadmap with clear milestones, priorities, and timelines. Focus on granular pieces rather than trying to update everything all at once.

Get everyone on board: ensure stakeholders, users, decision-makers, and especially the technical teams see the benefits and are buying into the work. A quick way to derail modernization is to not take care of your team or allow them to be impacted negatively.

Make wise technical choices for the right reasons: choosing a framework, language, or development methodology always has big pros and cons. Do the research to choose wisely and confidently, and guard against trend following, making assumptions, or being misinformed.

Healthy organizations are always working to modernize: application modernization is not a one-time event, and when completing a project, there is always another application that could benefit from modernizing. Show a bias for action and proactively look for your next modernization need. Don’t let inaction turn an application into a legacy application.

How Caylent can help

Application modernization is a big topic, and even the best checklist doesn’t guarantee results. Our Cloud Native Applications practice at Caylent can help you navigate and conquer the strategies and the pitfalls. We have helped our clients modernize applications, and we can help you achieve the application modernization goals and requirements you need for your business. As a Premier Tier AWS consulting partner and the AWS Innovation Partner of the Year, we are here to help you achieve great outcomes for your business.

We are forward-thinking technical experts, and we pride ourselves on true partnerships with our customers. Being a partner means engaging together in a focused effort to solve your problems, drive your vision forward, and achieve measurable technical and business results.

We are all in on AWS. We have deep expertise and knowledge, and your application modernization will be delivered by AWS certified architects and software engineers. 

We are trusted and proven. We consistently achieve 9.5+ CSAT scores with our clients, and we will bring this same level of excellence to your project.

We have broad industry specializations in the areas of SaaS, Healthcare, Life Sciences, Financial Services, Insurance, Education, and Transportation. 

Check out how Caylent can accelerate your application modernization journey and help you achieve your cloud native goals. We’d love to learn more about your business and application modernization goals.

Application Modernization
Chris Kemp

Chris Kemp

Chris Kemp is a Delivery Manager in the Cloud Native Applications practice at Caylent. He enjoys partnering with clients to implement AWS solutions using modern technologies and architectures. His many years in the software industry include application development, technical product management, team leadership, and co-founding a startup. Chris originally hails from the desert southwest but now calls the Dallas, TX area home. He strongly believes New Mexico green chile is the best condiment in the world, but has come to enjoy Tex-Mex too.

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