# Cutover Strategies > Source-anchored research for Cutover Strategies. Run status: COMPLETED. Parent: [MongoDB Migration Patterns](https://llms-explorer.com/tree/mongodb-migration-patterns/) · 2 facets · 8 facts · page: https://llms-explorer.com/tree/cutover-strategies/ ## Problems, failure modes and limitations - A short planned write pause can be safer when operators cannot verify replication integrity while writes remain live. LootLocker's postmortem describes in-flight changes lost by a replication process that appeared to recover, and says a planned validation window could have prevented the resulting data loss. (medium confidence) — [source](https://lootlocker.com/blog/db-postmortem-data-loss-during-database-migration/) - Moving tenants or components in phases can reduce the risk of a single large change, but it makes rollback a partial-system problem and can require extra write coordination. (low confidence) — [source](https://aws.amazon.com/blogs/database/rolling-back-from-a-migration-with-aws-dms/) - After cutover, a plain route back to the source can omit transactions written only to the target. Plan how to preserve post-cutover data, such as fail-forward replication, dual writes, or tested restore and replay, and define rollback checkpoints before the switch. The Azure utility documents an optional post-cutover sync-back path that replicates target changes to the source, followed by Restart Forward Sync before routing clients back; that path requires sync-back to be enabled at cutover. (high confidence) (verified as of 2026-10-23) — [source](https://docs.aws.amazon.com/prescriptive-guidance/latest/best-practices-migration-cutover/cutover-stage.html) ## Facts and statements - An online cutover can preload the target and continuously apply source changes, then perform a final catch-up before moving application traffic. This reduces the write interruption, but the final synchronization still needs a defined cutover window. (high confidence) — [source](https://www.percona.com/customer-story/off-atlas-onto-a-platform-that-scales-priceshapes-6-6-tb-move-to-percona-mongodb/) - EDB's MongoDB-to-Postgres guide says to stop MongoDB writes, run the final sync, validate critical data, switch connections, and keep MongoDB available for a 7–14 day rollback window. For mongosync moves between MongoDB clusters, MongoDB says to check for near-zero lag, stop writes to synced source collections and wait for source transactions to commit or abort before commit, verify the transfer before moving application workload, and treat COMMITTED as completion. Quest1 estimates its production write window at two to four hours and says it was held open only for final source-to-destination synchronization. After a data-loss incident, LootLocker recommended retaining the source until post-cutover validation is complete. (high confidence) — [source](https://www.enterprisedb.com/sites/default/files/pdf/Best_Practices_for_Non-Oracle_Migration.pdf) - After the target accepts writes, changing application routing back does not copy those writes to the source. A safe fast rollback therefore needs reverse replication or dual writes, or a deliberate write-freeze and recovery procedure; rehearse the reverse path before relying on it. (high confidence) — [source](https://aws.amazon.com/blogs/database/rolling-back-from-a-migration-with-aws-dms/) - For MongoDB online moves that use change-stream catch-up, treat cutover as a gated finalization: confirm low or near-zero lag, stop writes to the migrated source scope and let in-flight transactions finish, submit the commit, verify the successful sync and that destination writes are allowed before routing clients, and keep mongosync active until it reaches COMMITTED. The Azure Mongo migration utility similarly gates Cut Over on zero lag for every collection and completion of background index builds. (high confidence) (verified as of 2026-10-23) — [source](https://www.mongodb.com/docs/mongosync/current/reference/cutover-process/) - An all-at-once cutover moves every user with a single routing change, while a phased or canary cutover can expose a smaller slice, monitor load, and make routing rollback easier; phased cutover takes more coordination and time and requires dependencies that can split traffic. This does not remove the MongoDB data gate: for the collections included in a mongosync migration, stop source writes and verify the sync before clients use the destination. (high confidence) — [source](https://docs.aws.amazon.com/prescriptive-guidance/latest/best-practices-migration-cutover/cutover-stage.html)