Reclaim control from legacy bloat

Assess based on business urgency, system complexity, and ROI: rehost (lift-and-shift) for quick wins on stable, non-critical apps needing cloud scalability without changes. Refactor if the core logic is solid but UI/performance lags—wrap legacy in APIs and build OutSystems facades for gradual enhancement. Rebuild from scratch only for high-complexity, rigid systems where full redesign unlocks 5-10x agility; pilot a small domain first to validate. Prioritize by running Architecture Dashboard scores and user pain points.

Assess/inventory apps with AI Mentor/Discovery for dependencies and debt. 2. Define domains and pilot MVP screens in dual-run (old/new side-by-side). 3. Build API wrappers for legacy data, migrate high-traffic screens first via automation. 4. User-test iteratively with approvals before cutover. 5. Monitor via LifeTime, decommission old modules progressively. This phased approach ensures zero-downtime, typically 6-12 months for enterprise scale by focusing risk on small batches.

Layer OutSystems as a "strangler pattern" facade, expose legacy functions via stable APIs while rebuilding user-facing layers progressively, keeping core backend intact. Use reactive modules for new features, AI Mentor to flag/refactor spaghetti code, and domain-driven modules to isolate debt. This hybrid cuts maintenance 70% by offloading UI/logic to visual low-code, eases team upskilling, and allows phased retirement without big-bang risks.

Design a "bimodal" architecture: dedicated Integration Services module consumes legacy APIs/DB views, aggregates data, and exposes clean entities/actions to UI/Logic apps. Keep legacy as system-of-record (read-only where possible), use queues/timers for async syncs, and modularize by business domain. This decouples front-end agility from back-end stability, enabling parallel evolution and easy swaps later.

Create a thin API gateway module in OutSystems that calls legacy via secure connectors (JDBC for DB, SOAP/REST wrappers for mainframes), adding caching and throttling. Implement circuit breakers for resilience, encrypt sensitive calls with SSL, and version endpoints. Test with synthetic data first, monitor latencies in production—this shields modern apps from legacy volatility while enabling incremental replacement.

AI Mentor auto-detects migration candidates, generates reactive screens from legacy ones, and flags anti-patterns for 50% faster refactoring. Drag-drop visual dev replaces manual coding, pre-built connectors speed integrations 10x, and one-click deployment/publishing eliminates devops overhead. Teams deliver MVPs in weeks vs. years, iterating via citizen dev for UI while pros handle logic, proven to slash timelines via reuse and automation.

Key risks: data inconsistencies (mitigate with replication/validation timers), performance regressions (profile aggregates, use external DB indexes), and scope creep (fix via domain prioritization). User resistance, pilot with feedback loops; skill gaps—train via Forge accelerators. Start small, dual-run environments, and leverage ODC-readiness audits for long-term viability, ensuring 99.9% uptime.