Modernizing Mission-Critical Systems with Confidence: A Phased Coexistence Strategy

Modernization: The Opportunity—and the Risk

Modernizing mission-critical legacy systems promises remarkable gains. Forrester found enterprises can unlock up to 353% ROI, and research shows successful modernization can reduce IT costs by 45% and boost performance by 90%. Yet too many organizations fail to capture that value.

Why? Because modernization has traditionally required hard choices: maintain aging systems and risk falling behind—or attempt massive “big-bang” replacements that disrupt operations, introduce risk, and often fail.

Meanwhile, competitive pressures—from digital-first disruptors to AI initiatives—leave no room for delay.

That’s why OpenLegacy has pioneered a different approach: phased coexistence.

Modernize at Your Pace—Without the Risk

Instead of replacing entire systems overnight, phased coexistence allows enterprises to modernize incrementally. Legacy systems continue operating without disruption while selected functions, data, or processes transform into cloud-native services.

This approach:

• Reduces risk by avoiding sudden cutovers that jeopardize critical operations.
• Delivers fast ROI by unlocking value from each modernization step.
• Enables AI and cloud adoption early—even before all workloads migrate.
• Avoids middleware sprawl through direct, native connectivity between legacy and cloud.

OpenLegacy, in collaboration with AWS, makes this vision real. Our platform offers a unified modernization engine that bridges legacy systems and modern architectures—securely, automatically, and at enterprise scale.

“With the global reach of AWS and OpenLegacy’s innovative platform, we’re helping organizations worldwide transform legacy systems into competitive advantages.”
— Ron Rabinowitz, CEO, OpenLegacy

Inside the Phased Coexistence Framework

At the heart of OpenLegacy’s strategy is the OpenLegacy Hub, an AI-driven platform purpose-built for phased, structured modernization. It automates the discovery, analysis, and transformation of legacy systems into modern services.

Key pillars of the approach include:

The Unified Landing Zone

This provides a secure environment where legacy systems and cloud-native services coexist. Legacy processes remain undisturbed while new services deploy side-by-side.

• Expose legacy functions as modern REST, gRPC, or event APIs.
• Avoid the latency and cost of middleware.
• Simplify architecture while maintaining security and governance.

Dual Factory Model

Two engines work together to transform your legacy estate:

• Integration Factory: Automatically generates APIs from legacy code so new digital services can interact with existing systems without changes.
• Migration Factory: Modernizes code and data as you’re ready to move off legacy platforms.

Together, they ensure legacy and modern components stay connected throughout modernization.

AI-Driven Automation

Manual modernization takes years. OpenLegacy compresses timelines to weeks or months:

• Analyze legacy systems to pinpoint safe decoupling points.
• Auto-generate APIs, connectors, and test suites.
• Maintain compliance with automated testing and security checks.

This means modernization is no longer dependent on scarce mainframe experts—any IT team can lead the charge.

Decoupling Patterns: The Secret to Safe Modernization

A critical advantage of OpenLegacy’s coexistence approach is decoupling patterns—proven strategies that separate legacy systems into manageable pieces:

• Internal Decoupling: Replace rigid program-to-program calls with remote APIs, letting you modernize one module at a time while everything else runs unchanged.
• External Decoupling: Intercept gateway traffic (e.g., MQ, CTG, IMS) and redirect it to modern services, keeping legacy channels like green screens or ATMs operational.
• Data-Layer Decoupling: Move data to modern databases without rewriting COBOL logic by extracting embedded SQL into APIs.
• Logic-Layer Decoupling: Isolate business logic from legacy UI code to unlock reuse in digital channels and AI applications.
• Data Extraction & Sync: Enable real-time data flows between legacy and modern systems through Change Data Capture (CDC) and ETL.

These patterns let enterprises modernize only what’s necessary for the next step, reducing cost and risk.

Modernization in Action

Leading enterprises are already seeing transformative results:

• Legal & General modernized claims and document processing while maintaining core operations, delivering new services 8-10× faster.
• Raiffeisen Bank evolved from batch to real-time payments to comply with EU regulations—all without service disruption.
• Standard Chartered accelerated complex modernization projects from months to weeks, thanks to automated integration and testing.

Start Your Modernization Journey—With Confidence

The days of “rip and replace” are over. With OpenLegacy and AWS, enterprises can modernize confidently, preserve operational continuity, and unleash innovation.

Don’t wait to modernize your legacy estate—and don’t gamble your future on risky big-bang migrations.

Read our white paper, “Modernizing with Confidence: A Phased Coexistence Strategy for Legacy Transformation,” and discover how to transform at your pace, without the risk.