Integrating Automation with Legacy Systems: Patterns that Actually Work
Automation projects often face one hard truth: core systems are legacy, brittle, or undocumented. Success depends on integration patterns that respect the constraints of these systems while enabling modern automation.
This post presents practical patterns for integrating with legacy systems.
Strangling layers and adapters
Wrap legacy systems with an adapter layer that exposes a simple, well-documented API. This layer handles protocol translation, throttling, and retries.
The strangler pattern lets teams route new automation through the adapter while minimizing impact on the legacy system. Over time, the adapter can take on more responsibilities.
Event-driven facades
When direct synchronous integration is risky, use eventing: emit domain events that capture intent and let an adapter orchestrate interactions with legacy systems asynchronously. This reduces coupling and provides natural retry and compensation mechanisms.
Bulk transforms and safe windows
Legacy systems often have narrow windows for maintenance. Plan bulk data syncs during safe windows and design idempotent transforms. Use checkpoints and resumable transfers to avoid data corruption.
Human review for edge cases
When integration fails due to data quality or unexpected schema drift, route items to a human-in-the-loop process that can reconcile and resubmit with corrected context.
Observability
Instrument adapters and integration flows with rich logs, correlation IDs, and metrics. Correlation IDs are especially valuable for tracing a business transaction across modern and legacy components.
Conclusion
Integrating automation with legacy systems is a pragmatic exercise. Use adapters, events, and careful operational practices to protect both the legacy system and your automation investment.
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