Selling cutover is a phased migration method in which a new system starts handling fresh transactions before the legacy system is fully retired. Instead of switching everything at once, organizations “sell” new work into the replacement platform while older records, balances, or workflows are still being reconciled in the background.
This matters in cybersecurity because the overlap period creates extra risk: two systems may need to stay synchronized, access controls can differ between environments, and logging or monitoring gaps may hide mistakes. Attackers can abuse migration confusion to exploit duplicate accounts, stale permissions, or inconsistent data. Defenders use selling cutovers to reduce downtime, but they need strong change control, reconciliation checks, backups, and rollback plans. It is common in large business migrations such as airline, banking, and ERP transitions, where continuity is critical and even small data mismatches can disrupt operations.