An inventory proves that a server exists. It does not show which components must move together or which partner needs two weeks to update an allowlist. A one-page dependency map turns a list of assets into a migration sequence.
Follow one request end to end
Trace DNS, network controls, load balancing, applications, data stores and external APIs. Keep online requests, administration and batch work as separate flows.
Mark the source of truth
Show where writes are authorized, replication direction, tolerated lag and conflict rules. Files, indexes and caches can matter as much as the primary database.
Add external lead time and ownership
Record the partner contact, request process, test environment and typical change time for payments, messaging, logistics and identity connections.
Use the map to define waves
Group systems that must be validated together without making rollback unmanageably large. Attach cutover conditions, validation queries and the last safe rollback point to every wave.