As a software developer/solutions architect, navigating the complexities of modernizing legacy applications requires more than just adopting new technologies. It demands a deep understanding of software design patterns that ensure scalable, resilient, and maintainable solutions. Unfortunately, in the rush to modernize, crucial design patterns are often overlooked, leading to technical debt, performance bottlenecks, and security vulnerabilities. This article explores key design patterns frequently ignored by modernization teams, the reasons they are neglected, and the consequences of bypassing them. By integrating these patterns into modernization strategies, developers and architects can build robust, future-proof applications that stand the test of evolving technological landscapes.

Strangler Fig Pattern

The Strangler Fig Pattern is a gradual migration strategy where new functionality is built around the existing legacy system, slowly replacing it until the old system is entirely phased out.

• Why it’s overlooked: Modernization teams often opt for a full rewrite rather than incremental refactoring, assuming that starting from scratch will be faster and more efficient. However, this can introduce significant risks and delays.
• Real-world example: A financial institution migrating from a monolithic COBOL-based mainframe to a microservices-based architecture used the Strangler Fig Pattern. They introduced an API layer that progressively handled more transactions while legacy components were retired incrementally.
• Consequence of ignoring it: A complete system rewrite without this pattern can lead to prolonged development times, business disruptions, and increased failure risks due to untested new implementations.
• When to use: Use this pattern when modernizing large, complex legacy applications that cannot afford extended downtime or complete overhauls at once.

Saga Pattern

The Saga Pattern manages distributed transactions by breaking them into a series of smaller, compensating transactions.

• Why it’s overlooked: Modernization teams often assume eventual consistency is automatically handled by microservices frameworks, neglecting explicit transactional workflows. Implementing sagas can be challenging due to the need for handling failures and maintaining consistency. Teams may opt for simpler orchestration mechanisms without considering the potential for distributed transaction failures.
• A real-world example: An online travel booking system had issues where partial failures left customers with incomplete reservations (e.g., flights booked but hotels not confirmed). Implementing the Saga Pattern ensured rollback mechanisms were in place, maintaining data consistency across services. 
• Consequence of ignoring it: Without the Saga Pattern, distributed systems suffer from data inconsistencies, orphaned transactions, and poor user experience. Distributed transactions can lead to inconsistencies if not handled properly. Failures in one service can impact the entire transaction.
• When to use: Use this pattern when dealing with distributed transactions involving multiple services that must maintain consistency and systems with complex business transactions that span multiple services.

Sidecar Pattern

The Sidecar Pattern runs auxiliary services in separate containers alongside main application services, enabling functionalities like logging, monitoring, and security without modifying the core application.

• Why It’s Overlooked: Modernization teams may prioritize core service development and neglect auxiliary concerns, leading to bloated application code.
• Real-World Example: A fintech company used the Sidecar Pattern to deploy a separate logging and monitoring service alongside each microservice, simplifying debugging and performance tracking.
• Consequence of Ignoring It: Neglecting this pattern leads to tightly coupled services, making maintenance difficult and increasing the complexity of scaling and updating auxiliary functions.
• When to Use: Use this pattern when microservices require independent functionalities like logging, monitoring, or security without modifying the core service logic.

Circuit Breaker Pattern

The Circuit Breaker Pattern prevents a system from continuously making requests to a failing service, reducing unnecessary load and enabling faster recovery.

• Why it’s overlooked: Modernization teams often assume cloud-native platforms handle failure gracefully, ignoring the need for explicit fault tolerance mechanisms.
• Real-world example: Netflix employs the Circuit Breaker Pattern to maintain high availability in its microservices architecture. If a particular service fails repeatedly, the circuit breaker trips and prevents further calls until recovery.
• Consequence of ignoring it: Without circuit breakers, cascading failures can occur, where a single failing microservice can bring down an entire system due to unhandled retries and excessive load.
• When to use: Use this pattern in distributed systems where service failures must be isolated to prevent widespread outages.

Bulkhead Pattern

The Bulkhead Pattern isolates different components or services so that failures in one do not impact the others.

• Why it’s overlooked: Many teams focus on horizontal scaling but neglect to compartmentalize workloads, making services susceptible to systemic failures.
• Real-world example: In e-commerce platforms, checkout, inventory, and recommendation services can be isolated using bulkheads to ensure that failure in one does not affect the others.
• Consequence of ignoring it: Ignoring this pattern can lead to entire systems going down due to a single point of failure, significantly impacting user experience and revenue.
• When to use: Use this pattern in microservices architectures where services must operate independently to ensure resilience.

Event Sourcing Pattern

The Event Sourcing Pattern stores changes to an application’s state as a sequence of immutable events rather than modifying records directly.

• Why it’s overlooked: Teams often prioritize relational database models and transactional consistency, overlooking event-driven architectures that enhance auditability and scalability.
• Real-world example: Uber uses event sourcing to track rides, payments, and user interactions, ensuring that every action is recorded as an event for consistency and debugging.
• Consequence of ignoring it: Not using event sourcing can lead to data inconsistencies, loss of historical data, and difficulties in troubleshooting and replaying past transactions.
• When to use: Use this pattern in applications requiring strong audit trails, historical tracking, and event-driven state management.

CQRS (Command Query Responsibility Segregation) Pattern

CQRS pattern separates read and write operations into different models, optimizing for performance and scalability.

• Why it’s overlooked: Many teams’ default to CRUD-based architectures without considering read-heavy or write-heavy optimizations.
• Real-world example: E-commerce platforms like Amazon use CQRS to manage inventory updates separately from customer queries, ensuring high performance under heavy loads.
• Consequence of ignoring it: Ignoring CQRS can lead to database contention, performance bottlenecks, and inefficient scaling strategies.
• When to use: Use CQRS in high-performance applications where read and write workloads differ significantly.

Repository Pattern

The Repository Pattern separates the business logic from data access, providing a clean abstraction layer between application logic and database queries.

• Why It’s Overlooked: Modern ORM (Object-Relational Mapping) frameworks promise simplified data management, leading teams to believe explicit repository layers are unnecessary.
• Real-World Example: A healthcare software provider initially used direct ORM calls within service classes. As the system scaled, database logic became scattered, leading to maintenance challenges. Refactoring to use the Repository Pattern improved code organization and maintainability.
• Consequence of Ignoring It: Ignoring this pattern leads to tightly coupled code, making it harder to switch databases, optimize queries, or maintain separation of concerns.
• When to Use: Use this pattern when dealing with complex domain logic that requires a clean separation between business rules and data access.

API Gateway Pattern

The API Gateway Pattern acts as a single entry point for all client requests, routing them to appropriate backend services while handling cross-cutting concerns like authentication, logging, and rate limiting.

• Why It’s Overlooked: Teams may assume direct client-to-microservice communication is sufficient, leading to complex client logic and inefficient network calls.
• Real-World Example: A streaming service adopted an API Gateway to handle authentication, request aggregation, and traffic management across various backend services, improving performance and security.
• Consequence of Ignoring It: Without an API Gateway, microservices architectures can become fragmented, increasing security risks, inconsistent data access, and complex client-side logic.
• When to Use: Use this pattern when managing multiple microservices and requiring centralized handling of security, authentication, and request routing.

Modernization efforts should not only focus on adopting new technologies but also on leveraging proven design patterns to ensure scalability, resilience, and maintainability. Patterns like Strangler Fig, Saga, Circuit Breaker, Bulkhead, Event Sourcing, Repository, Sidecar, and CQRS provide essential strategies to ensure a scalable, resilient, and maintainable architecture. By integrating these patterns into modernization efforts, teams can avoid common pitfalls, minimize risks, improve system reliability, and create robust solutions for the future.

A version of this blog was first posted by Karsun expert Lakshman Maruri. Lakshman is an expert in our aviation portfolio. Connect with him on LinkedIn. Our Karsun Cloud Solutions experts use tools like those available in our Cloud Runways and Microservices Toolkits to accelerate transformation and build resilient, scalable architecture. Learn more at https://karsun-llc.com/innovation-center/modernization-and-transformation-toolkits/cloud-runways/

For many organizations, an Amazon Web Services (AWS) Competency is table stakes. In fact, Canalys released a report revealing that organizations with AWS Specializations, including competencies, unlock $315 billion in customer spending. Moreover, 87% of customers surveyed ranked specializations among the top three selection criteria. For the Amazon Partner Network (APN) partners that achieve these designations, it signifies their expertise, commitment to industry best practices, and ability to deliver solutions seamlessly on AWS. For competency partners, it also presents new opportunities to leverage AWS resources to empower their customers as they migrate to the cloud and accelerate technology adoption.

Migration Incentives

An AWS Competency more than differentiates partners based on their expertise and experience. It also opens up new opportunities to support customer modernization efforts. A 2022 Canalys Partner Ecosystem Multiplier study found that for every dollar of AWS infrastructure sold, there is up to $6.40 available to partners to deliver services to customers. 

For example, Karsun achieved its AWS Migration Competency in 2021. As a result of this designation, Karsun teams could use AWS Migration Acceleration Program (MAP) resources. This comprehensive program packages best practices, tools, expertise, and financial incentives to make cloud adoption easier. When applicable, Karsun implements these financial incentives as part of its Cloud Runways toolkit, which accelerates cloud migration through fit-to-purpose transformation playbooks. These enable incremental migrations that adapt to unique customer requirements and constraints.

Technology Acceleration

A government information technology contractor with more than a decade of experience serving U.S. government agencies, Karsun achieved its Government Competency status in 2019. The competency differentiates AWS Partner Network (APN) members serving government agencies with deep domain expertise in security and compliance, in addition to innovative cloud solutions that leverage AWS services. 

In a recent video, Karsun Innovation Center Senior Vice President Badri Sriraman shares his experience integrating emerging technology with the resources available to AWS government competency partners. Filmed at the AWS Washington, D.C. Summit Government Competency Leadership Circle, Sriraman discusses how his team used tools from AWS to accelerate Karsun’s AI toolkit, ReDuX AI. Powered by AWS Bedrock, ReDuX AI uses analysis generative AI to perform code analysis, provide recommendations, and generate code for teams working on mainframe modernization projects. To learn more about ReDuX AI, visit GoReDuX.AI.

Video

AWS Government Competency Accelerates AI Research and Development

Karsun Innovation Center Badri Sriraman shares his experience at the AWS Government Competency Leadership Circle at the 2024 AWS Summit Washington, D.C.

In addition to migration and technology benefits, competency partners have access to specialized training, industry events, and support from AWS experts. Partners with AWS Specializations have a wealth of opportunities to support their customers’ modernization ambitions. Overall, the partners that have obtained AWS Competencies significantly enhanced their ability to deliver high-quality AWS solutions.

Karsun is among those partners using the full range of resources available to it as it serves its agency customers.  It elevates agency capabilities through modern software development, cloud, data, and AI solutions. Its cloud portfolio offers a full suite of solutions, including hybrid architecture, platform buildout, and application migration. It has AWS Government, Migration, and DevOps Competencies and is a Well-Architected Partner. To dive into Karsun’s complete cloud solutions portfolio, visit https://karsun-llc.com/solutions/cloud-solutions/.

HERNDON, VA – Karsun Solutions announced it achieved Amazon Web Services (AWS) Well-Architected Partner Program status. Karsun delivers enterprise modernization solutions to federal civilian government agencies. Its software development, cloud and data solutions teams all deliver on AWS.

The AWS Well-Architected Framework helps cloud architects build and operate secure, high-performing, resilient, and efficient application infrastructures. Based on six pillars, operational excellence, security, reliability, performance efficiency, cost optimization, and sustainability, it provides a consistent way to evaluate architectures and implement designs that will scale with application needs over time. AWS Well-Architected Partners like Karsun can help customers measure the state of their workloads, recommend improvements, and implement best practices.

“Adoption of the AWS Well-Architected principles is part of Karsun’s ongoing commitment to delivering digital architecture built to last,” said Badri Sriraman, Senior Vice President of the Karsun Innovation Center.

Karsun Solutions is an AWS Advanced Tier Services Partner and AWS Public Sector Partner with AWS Government Competency, AWS Migration Competency and AWS DevOps Competency designations. With AWS Migration Competency status, Karsun’s customers may utilize the company’s access to AWS Migration Acceleration Program (MAP) resources. When applicable, Karsun implements these financial incentives as part of AWS MAP. Its government customers may also leverage Karsun’s extensive experience modernizing large, complex systems with Cloud Runways, a portfolio of purpose-built toolkits optimizing migration to the cloud. Learn more about Karsun’s AWS Practice at https://karsun-llc.com/about/partners/aws/.

About Karsun Solutions

Karsun Solutions modernizes enterprise systems enabling agencies to make the next technological advancement their next opportunity to elevate mission capability. IT solutions from Karsun are tailored to meet agencies’ unique needs and optimize operations. These solutions adapt and stay relevant with current trends while using secure, digital architecture built to last. It is a proven modernization partner whose expertise elevates agency capabilities and ensures every next opportunity is within reach.

Company Contact: marketing@karsun-llc.com

HERNDON, VA– Karsun Solutions, the Enterprise Modernization Experts, announced today that it has achieved Amazon Web Services (AWS) Migration Competency status. This designation recognizes that Karsun Solutions provides deep expertise to help customer’s move successfully to AWS, through all phases of complex migration projects, discovery, planning, migration and operations.

Achieving the AWS Migration Competency differentiates Karsun Solutions as an AWS Partner that provides specialized demonstrated technical proficiency and proven customer success with specific focus on Migration Delivery and Migration Consulting. To receive the designation, AWS Partners must possess deep AWS expertise and deliver solutions seamlessly on AWS.

“Karsun Solutions is proud to achieve AWS Migration Competency status,” said Kartik Mecheri, Karsun Solutions Co-Founder. “It is a perfect reflection of our work as modernization experts and our team is dedicated to helping companies achieve their technology goals by leveraging the agility, breadth of services, and pace of innovation that AWS provides.”

AWS enables scalable, flexible, and cost-effective solutions from startups to global enterprises. To support the seamless integration and deployment of these solutions, AWS established the AWS Competency Program to help customers identify Consulting and Technology AWS Partners with deep industry experience and expertise.

The Karsun Solutions Cloud Migration portfolio offers clients a full suite of services to develop and host cloud-based applications. Backed by the AWS Migration Competency, its customers may also utilize Karsun’s access to AWS Migration Acceleration Program (MAP) resources.

AWS MAP is a comprehensive and proven cloud migration program based upon AWS’s experience of migrating a thousand enterprise customers to the cloud. The program packages best practices, tools, expertise, financial incentives, and the AWS Partner Network (APN) to make cloud adoption easier. Supporting customers investigating migration solutions, these financial incentives subsidize the three key steps in the migration process (Assess, Mobilize, and Migrate and Modernize). When applicable, Karsun implements these financial incentives as part of its Cloud Runways toolkit which accelerates cloud migration through fit-to-purpose transformation playbooks. These enable incremental migrations which adapt to unique customer requirements and constraints.

The data driven migration approach used by Karsun Solutions assesses the existing integration landscape, identifies future needs and develops future state integration architecture, with a specific focus on harmonizing information across applications. Using a proprietary multi-criteria decision support framework, the platform team performs a robust assessment of the solution identifying key characteristics such as interoperability, flexibility, SLAs and security to make an optimal selection for its customers. The framework also balances private, public and hybrid cloud options based on economics, functionality and security.

In addition to the AWS Migration Competency, Karsun Solutions also achieved the AWS Government Competency designation. It currently serves agencies including the Department of Homeland Security (DHS), the Federal Aviation Administration (FAA) and the General Services Administration (GSA). Karsun’s public sector AWS cloud migration case studies are available at https://karsun-llc.com/solutions/cloud-solutions/aws-cloud-migration/.

About Karsun Solutions

Karsun Solutions is a fast-growing, innovative, enterprise modernization firm. Recently named a Technology Industry Top Workplace, its teams deliver modern software development, cloud, and data solutions to customers at government agencies including DHS, FAA and GSA. The Virginia Chamber of Commerce, Washington Business Journal, and Inc. all recognize Karsun Solutions among the fastest-growing companies in the Washington, D.C. region. An established firm with a DCAA Approved Accounting System and CMMI Level 5 – DEV appraisal, plus both the AWS Government Competency and AWS Migration Competency designations, it holds ISO 9001, ISO 20000 and ISO 27001 certifications.

Media Contact

marketing@karsun-llc.com

Karsun Solutions offers a portfolio of enterprise modernization solutions to federal and commercial clients. Key among these is Karsun’s cloud migration solution, Cloud Runway. Cloud Runway enables cloud first organizations to migrate legacy systems to the cloud. Karsun recently paired its Innovation Center team with one of their federal customers for a large migration effort using Amazon Web Services (AWS).

The Challenge

The customer approached Karsun to move an app to the cloud in order to reduce costs. Critically, the customer also wanted to limit the impact on business lines during the migration. In any of Karsun’s Cloud Solutions offerings, the goal is to leverage the flexibility and agility offered by the cloud to reduce costs. The approach balances private, public, and hybrid cloud options based on economics, functionality, and security. Migration teams use strategic partnerships, like those with AWS, to build cost-effective high-quality solutions.

Beginning the Transformation Process

Karsun’s Cloud Runaway leverages change management best practices. Migration teams discourage customers from building their own platforms in favor of focusing on the assets and processes already available to them. They start by identifying the processes and tools already in use. First, the team implements Karsun’s GoLean methodology. Teams identify daily process performance and health measures prior to migration. These measures are assessed and tracked throughout the migration to observe and mitigate the impact on development teams.

Once teams are actively measuring their performance metrics, tools are paired with similar cloud-native apps. The objective is to support and nurture the processes already in place. Karsun’s partnership with AWS supports the migration team’s efforts to use their own experience to select the most appropriate tools available. Cloud Runway takes a collaborative to this transition. The Karsun Innovation Center pairs one of its teams with the migration team. In bringing this in-house research and development team on board, the migration effort utilizes the latest enterprise architecture solutions.

Combining Karsun’s change management approach with strategic cloud partnerships, the customer was able to quickly migrate to the cloud with limited interruptions to their business lines. Explore our Cloud Solutions page for more including customer case studies. Contact Us to start a conversation with our cloud migration team.