Decide where authoritative records live and document how other systems derive views from them. Resist duplicating mutable data without reconciliation plans. Even a spreadsheet can serve as the canonical roster if updates are logged, validated, and broadcast consistently, preventing silent divergence that sabotages dashboards and confuses customers unexpectedly.
Emit events for meaningful state changes, not every checkbox click. Consumers subscribe, translate, and act without tight dependencies on producers. This keeps pieces replaceable and testing focused. When a billing provider changed webhooks, only one adapter broke, not the entire workflow, saving hours and protecting end-of-month revenue.
Plan for hiccups: network timeouts, duplicate deliveries, and partial updates. Implement retries with exponential backoff, deduplicate by unique keys, and log correlation IDs for tracing. Teams sleep better when failures are expected, explained, and recoverable without heroic midnight sessions or manual database edits that risk bigger damage.
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