Coordinate Vitess Online DDL across every shard of a keyspace. Submits with --postpone-completion, holds a global cutover barrier until all shards report ready and none is lagging, then completes them together — turning per-shard schema skew into zero. Live progress, throttle guard, revert, resumable journal, and a deterministic cluster simulator.

Plan and sequence Vitess resharding offline. Key-range algebra, minimal Reshard workflow computation from source/target layouts, VSchema and topology preflight, VReplication duration estimates, and a step-by-step operator runbook with verification and rollback for every step. Dry-runs plans in CI.