MODX zero-downtime migration and modCache invalidation timing

A small MODX application needs to be moved to new hosting with no perceptible downtime. The plan relies on database-level synchronization of the nested resource tree and a final DNS cut-over, with the existing site remaining writable until the switch.

The constraints are the relational resource tree in MODX, the modCache fragment caching system, and a plugin-based hook architecture that fires on resource save. Uncertainty exists about how cache state and tree integrity behave when the source and target are briefly writable in parallel during the final sync window.

Does MODX provide a documented global invalidation point for modCache fragments when the database is switched under load? Which mechanism controls whether stale cached fragments can be served from the target after cut-over if cache tables are not replicated? Is the resource table update atomic under high-concurrency writes during a live sync, or can tree-index mismatches arise without explicit locking?