I built a small CDN data path around the S3-compatible contract shared by AWS S3, Cloudflare R2, and MinIO to explore cache identity, request collapsing, revalidation, byte ranges, and the line between a caching proxy and a CDN.
Once integrations become business-critical, the work is no longer just calling APIs. Reliable integration systems need boundaries, state, failure handling, idempotency, observability, operations, and auditability.
Bidirectional sync turns integration into an authority problem. Reliable systems need field ownership, conflict detection, event history, reconciliation, and explainable state.
External systems do not fail only during outages. They drift, evolve, and quietly violate the assumptions your product has turned into invariants.