AWS re:Invent 2025 -Monolith to Microservices: A Field Tested Accelerated Path to True Modernization

Modernizing Legacy Systems with MongoDB's Application Modernization Platform

Overview

• Jay Wrl, a distinguished solution architect at MongoDB, presents the company's approach to rapidly modernizing legacy systems to MongoDB.
• The key focus is on transitioning monolithic applications built on relational databases (e.g., Oracle, SQL Server) to a microservices architecture on MongoDB.

Challenges of Legacy Modernization

• Legacy systems are often highly complex, with:
  • Thousands of lines of code, stored procedures, and user screens
  • Outdated technologies (e.g., JBoss, WebSphere, .NET)
  • Tightly coupled components (database, ORM, caching, business logic)
  • Technical debt accumulated over decades of patches and hacks
• Lifting and shifting these monoliths to the cloud does not solve the underlying issues.
• Attempting to use generative AI (e.g., ChatGPT) for direct code translation often fails due to the complexity of the legacy codebase.

MongoDB's Application Modernization Platform

• Combines custom tools, methodologies, and expert teams to accelerate the modernization process.
• Key components:
  1. Analysis: Comprehensive analysis of the legacy codebase to understand dependencies and plan the modernization journey.
  2. Test Coverage: Automated generation of test cases to ensure correctness of the modernized application.
  3. Transformation: Incremental translation of legacy code (e.g., PL/SQL to Java) with immediate testing.
  4. Side-by-Side Testing: Validation of the modernized application by comparing inputs, outputs, and database state changes against the legacy system.
• Automation is a key focus, with custom Python scripts and GUI tools to manage the end-to-end process.

Methodology: The Application Transformation Framework

• MongoDB has developed a documented methodology, the "Application Transformation Framework," based on lessons learned from past modernization projects.
• The framework provides guidance on the optimal steps and tools for different modernization tasks (e.g., PL/SQL to Java, database migration).
• Ensures consistency and leverages the collective experience across the company's modernization teams.

Customer Success Stories

1. Lombard Odier (Swiss Bank):

   • Accelerated the modernization journey from 6-7 years to a significantly faster timeline.
   • Achieved 2-3x productivity improvements in areas like test coverage generation, data access layer migration, and runtime upgrades.

2. Bendigo Bank (Australia):

   • Realized a 63% improvement in the modernization project timeline by leveraging MongoDB's Application Modernization Platform.

Key Takeaways

• Modernizing legacy systems is a complex challenge that requires a comprehensive, methodical approach.
• Generative AI alone is not sufficient for directly translating large, mission-critical legacy codebases.
• MongoDB's Application Modernization Platform combines custom tools, proven methodologies, and expert teams to accelerate the modernization process.
• The platform's focus on analysis, test coverage, incremental transformation, and side-by-side validation helps overcome the challenges of legacy system complexity.
• Documented frameworks and consistent methodologies enable MongoDB to leverage lessons learned across multiple customer engagements.
• Customers have seen significant improvements in modernization timelines and productivity by partnering with MongoDB.