Choosing Between Deferred and Immediate Index Builds for Rollback Safety

Goal: Safe Rollback After Schema Change

When applying a schema change via N1QL index updates in Couchbase, the objective is to allow a rollback to the previous index version without causing query downtime or excessive resource spikes. The two documented approaches are to create the replacement index with the WITH deferred clause and later trigger a BUILD INDEX, or to create it immediately (no deferred flag) so it builds synchronously.

Unresolved Resource Contention

• Does a deferred index build, initiated by BUILD INDEX, impose a more predictable I/O pattern during heavy write loads compared to an immediate build?
• How does the transition from deferred to active state affect mutation latency when foreground write traffic is at peak?
• What mechanisms, if any, let administrators prioritize foreground mutations over background index construction to preserve rollback safety?