App Modernization Framework: Transforming On-Prem Legacy Systems with Google Distributed Cloud

Guest contributor

Giri Padmanabh, Founder , CTO AppFaktors

Executive summary

Legacy application modernization is critical for business agility, security, and cost efficiency. Organizations with outdated on-prem software experience higher operational costs, security vulnerabilities, and scalability limitations. Research from Gartner (2024) indicates that 75 percent of enterprises will have embarked on application modernization by 2025 — but many will struggle due to unclear strategies and complex migrations.

This white paper outlines a structured approach to application modernization, addressing key challenges and providing actionable strategies for successful implementation.

Key takeaways

• Comprehensive modernization framework
• Implementation best practices
• Success metrics and KPIs

Introduction

Market context

Cloud adoption and digital transformation have become business-critical, with enterprises shifting to cloud-native architectures for agility and cost savings. Legacy applications, while functional, often hinder innovation and agility. According to recent studies:

What is application modernization?

Application modernization is the process of converting, rewriting or porting legacy software applications to operate more efficiently with a modern cloud infrastructure. This can involve migrating to the cloud, creating apps with a serverless architecture, containerizing services with modern DevOps models and delivering continuous authority to operate (cATO) within highly regulated environments.

The benefits of application modernization

• Cloud-native modernization reduces infrastructure costs by up to 40 percent while improving performance and scalability. Enterprises that migrate to Google Cloud and Google Distributed Cloud (GDC) report faster time to market and lower operational overhead.
• Refactoring a database from an older technology to a cloud managed modern alternative not only enables new features and reduces toil, but also makes it secured and compliant.
• Orchestration and container technologies like Docker and Kubernetes allow enterprises to spool and decommission resources as needed. Further aiding in the automation of release management and change.
• Converting legacy apps to new infrastructure enables data-driven analytics, and automation workflows or playbooks to increase operational efficiencies.

Business drivers

Organizations pursue modernization to achieve multiple objectives:

Strategic approaches

Choose one of the following approaches based on your business demands:

• Incremental modernization: A phased transformation approach that emphasizes risk mitigation and business continuity through gradual adoption of new technologies and processes. This iterative approach is often used in large scale migrations, where an event, such as vacating an existing data center, drives large volume activity over individual refactoring activity.
• Transformative modernization: A complete architectural redesign focused on cloud-native principles and modern technology adoption, following a digital-first approach for comprehensive transformation. This application modernization approach is often driven via a portfolio maturity effort, rather than large scale migrations.

Modernization patterns

Organizations can choose from several modernization patterns based on their specific needs and constraints:

What does an application modernization involve?

Application modernization process starts with Application Portfolio Optimization. The modernization journey requires a well-defined strategy that aligns with business objectives while managing risks and ensuring continuity. Before selecting cloud platforms or technical solutions, organizations must first map and analyze their existing application portfolio. The strategy should prioritize business needs over technology choices, ensuring a future-proof modernization approach.

5-step journey for application modernization

1. Application portfolio discovery
2. Application assessment and portfolio optimization
3. Architecture development
4. Pre-ATO and implementation
5. Architecture observability

Let's explore each step in more detail.

1. Application portfolio discovery

Initial inventory collection

Objective: Establish a single source of truth for all applications and IT infrastructure.

1. Application layer: Identify programming languages, frameworks, runtime environments and tools in use.
2. Infrastructure layer: Map out OS, middleware, storage and security dependencies.
3. Data layer: Document data architecture including sensitivity classifications, security protocols, data flow patterns, database systems, volume requirements, external data services and data warehouse implementations that form the data ecosystem.
4. Integration layer: Map system interconnections including external system interfaces, API dependencies, data exchange patterns, authentication mechanisms and trust zones of external systems that enable seamless integration.

Inventory collection methods

Automated discovery tools

Primary purpose:

• Automated discovery from SaaS and cloud APIs.

Analysis and extraction from prior documents

Primary purpose:

• Reverse engineering of architecture from past KB sources.
• Reverse engineer architecture from prior architecture and operations docs.

Manual discovery process using surveys

Primary purpose:

• Survey stakeholders for application tribal knowledge.
• Design a structured stakeholder engagement through targeted surveys, focusing on identifying current pain points, and critical functionalities that are essential for system operations.

2. Application assessment and portfolio optimization

A comprehensive assessment forms the foundation of successful modernization. Establishing clear application scoring criteria.

Assessment

1. Application architecture assessment: Evaluate application's technical foundation, architecture patterns, scalability capabilities, performance characteristics, resilience features and security mechanisms to determine modernization readiness.

2. Technical architecture assessment: Evaluate infrastructure readiness for modernization:

3. Dataflow architecture assessment: Examine system integrations, analyzing external system dependencies, data exchange patterns, authentication mechanisms and trust zones of external systems to ensure secure and efficient data flow.

4. Cloud readiness assessment: Evaluate cloud migration preparedness, examining container readiness, API compatibility, data portability, and security compliance, while assessing architecture compatibility, infrastructure requirements and service dependencies.

5. Business impact assessment: Value stream analysis provides good insights into user impact and strategic alignment based on business process importance, technology dependency, revenue dependency and regulatory requirements.

Each assessment component contributes to a holistic understanding of both technical feasibility and business value in the modernization journey.

Portfolio optimization

1. Application categorization: Use a strategic classification framework that assigns appropriate migration strategies to applications, determining suitable candidates for rehosting, identifying re-platform opportunities, defining refactor requirements and evaluating replace/retire options based on technical and business criteria.

2. Prioritization framework: Define a structured approach to migration sequencing based on critical factors including business value contribution, technical risk assessment, migration complexity evaluation and resource requirement analysis to optimize the modernization roadmap.

3. Architecture development

Target architecture:

• Cloud-native architecture: Create a modern architectural approach leveraging containerization, orchestration, service mesh implementation and API gateway patterns to ensure scalable and resilient cloud operations.
• Microservices architecture: Design a distributed architectural pattern focusing on service decomposition, robust API design, event-driven communication patterns, and efficient state management to enable application agility and maintainability.
• Cloud architecture design: Create a comprehensive digital architectural framework encompassing application design, infrastructure implementation, security controls and network topology to create a robust and secure cloud environment optimized for modern workloads.

4. Pre-ATO implementation

1. Implementation approach:

• Preparation: This phase includes strategic team formation, tool selection, environment setup, and clear process definition to ensure implementation readiness.
• Execution: Create a systematic implementation process including migration execution, thorough testing and validation, performance optimization, and security implementation to ensure successful deployment

2.  Technical implementation: Use standardized migration templates based on modernization strategy:

3. Operational framework: Define a comprehensive operations model defining operational procedures, support structures, monitoring frameworks, and incident management processes to ensure sustainable application management.

5. Architecture observability

Once the application is operational, it is very important to continually align operational service with business goals. By observing architecture drifts continually, application services can be governed well for risk and costs. In the case of Federal Government requirements, this translates to ConMon services, POAM activity and continuous ATO ops with integrated management stacks capable of OSCAL-based reporting to ATO authorities.

Governance planning

Risk mitigation: Put in place a robust governance structure establishing decision frameworks, policy management processes, compliance controls, and risk management strategies to maintain operational integrity and regulatory compliance.

Financial planning

Cost structure: Cost planning for modernization:

• Migration costs: One-time expenses for rehosting, re-platforming or refactoring.
• Operational costs: Ongoing cloud services, infrastructure and support.
• Personnel and training: Upskilling costs for DevOps, security and cloud teams.

Value tracking: Define value streams to measure return on investment through quantifiable metrics including cost savings realization, performance improvement measurements, business benefit achievement and innovation value creation across the modernization journey.

Mitigation strategies and best practices

Application portfolio discovery

Effective risk management prevents modernization failures. Organizations should:

• Identify risks early (security, cost, downtime).
• Apply structured mitigation (encryption, IAM, disaster recovery).
• Continuously monitor for architecture drift and compliance gaps.

Security risks in modernization:

• Data exposure: Legacy applications often store sensitive data in outdated encryption standards.
• Insufficient identity management: Migrating apps without properly integrating IAM can lead to access control gaps.
• Compliance failures: Some architectures may not meet industry-specific regulations.

Operational risks in modernization:

• Service downtime: Poor migration planning can result in extended outages.
• Unexpected cost increases: Resource misallocation can lead to excessive costs.

Success metrics

Best practices

Since the application modernization involves critical applications which are already valuable to business, there cannot be any downtime and delays.

Strategic planning: Architecture development should emphasize clear objective definition, stakeholder alignment, detailed architectural views, architecturally significant requirements, risk mitigation plan and thorough reviews for setting realistic timeline development, and resource planning to ensure modernization success.

Implementation success: Apply architecture driven DevOps practices to track the architecture roadmap with DevOps tasks status for regular validation processes, continuous monitoring practices, and effective knowledge transfer to ensure sustainable modernization outcomes.

Google Distributed Cloud (GDC) advantages

Whether managing and running apps in the cloud, on-premise or a hybrid environment, Google Cloud provides the proven tools for infrastructure provisioning, orchestration, security, networking, automation and monitoring.

Modernization for air-gapped environments

In certain industries and government agencies operations occur under stringent security and compliance requirements, often necessitating air-gapped environments that isolate critical systems and data from the public internet. This presents a unique challenge: how to achieve application modernization and migration goals while adhering to strict isolation protocols?

Google Distributed Cloud (GDC) offers a compelling solution, extending the power and flexibility of Google Cloud into environments where connectivity is limited or non-existent. GDC enables organizations to modernize and migrate applications within their own data centers, edge locations and, crucially, within air-gapped environments. GDC's air-gapped offering brings a curated suite of Google Cloud services directly into the isolated environment, allowing organizations to leverage familiar tools and technologies.

Google, WWT and AppFaktors understand that a successful implementation requires not only the right technology but also a deep understanding of the unique operational and compliance considerations.

Our insights are grounded in practical experience supporting the key personas involved in GDC air-gapped deployments — the Infrastructure Operator, the Platform Administrator and the Application Operator — ensuring that the recommendations and best practices presented are practical and effective.

Furthermore, we recognize the importance of organizational structure and workflows within these environments, including the need for separation of duties, 24x7 staffing models, and multi-party approvals for changes.

GDC air-gapped facilitates:

Containerization and orchestration: Leveraging Kubernetes-based platforms like Google Kubernetes Engine (GKE) within the air-gapped environment enables the deployment and management of containerized applications, promoting portability, scalability and efficient resource utilization.

Serverless computing: GDC air-gapped supports serverless platforms like Cloud Run, allowing developers to focus on code rather than infrastructure management, simplifying development and deployment.

Data management and analytics: Bringing Google Cloud's robust data management capabilities into the air-gapped environment empowers organizations to leverage their data for insights and decision-making. This includes options for deploying databases, data warehousing solutions and analytics tools, all within the isolated setting.

Modern development tools: GDC air-gapped provides access to a suite of modern development tools and APIs, enabling developers to build, test and deploy applications efficiently. This includes familiar programming languages, frameworks and CI/CD pipelines.

WWT advantages

While most organizations have embraced a cloud operating model, a significant number grapple with unlocking cloud's extensive capabilities. That's because optimizing cloud environments has become more complex than ever.

We believe today's digital world demands a new approach. One where your people, processes and technology operate in harmony. Where it's easy to achieve the visibility and resiliency needed to scale cloud at the speed of your business or mission. Our services enable cloud adoption at mission speed and offer numerous benefits, such as:

For highly regulated environments, WWT provides platform support for GDC air-gapped clouds. This supports secure environments, such as Secret and Top Secret.

AppFaktors advantages

Not all modernization tools are built for enterprise-scale complexity. AppFaktors goes beyond basic application tracking by automating portfolio optimization, integrating architecture as code (AaC), and embedding threat modeling from day one.

Why enterprises choose AppFaktors over alternatives:

• Accelerate modernization initiatives by automating application portfolio optimization.
• Cut architecture development time by 50 percent through automated processes.
• 50 percent faster architecture decision-making through AI-driven insights.
• Improve efficiency and reduce misinterpretation by streamlining collaboration between architecture, development, and operations teams through live digital architecture.
• Eliminates 90 percent of security risks at the design stage via built-in threat modeling.
• Cuts cloud waste by up to 30 percent and maintain efficiencies through quarterly workload well-architected assessments and optimization using builtin assessment manager.

When security, speed and cost matter — AppFaktors delivers.

Conclusion

Application modernization is no longer optional — organizations that fail to adapt risk losing agility, security and competitive advantage. Success requires a well-planned strategy, robust implementation approach, and continuous focus on business value and risk management.

References

• Gartner (2024). "Application Modernization Trends"
• IDC (2024). "Digital Transformation Insights"
• Google "Cloud Migration Center"

*About the authors: This white paper was developed by a team of enterprise architects and digital transformation experts with extensive experience in application modernization initiatives.

Reviewed by: Steven Swapp, Partner Engineer, Google; and Zaid Elkhateeb, Technical Solutions Architect - WWT.