For the avoidance of doubt, one of the key design principles of MongoDB Atlas is that all changes to database clusters are made in a rolling manner preserving majority quorum (save for a momentary election of at the replica set level) and hence uptime throughout: This means that changing from provisioned IOPS to general storage is a no downtime operation assuming your application is engineered to withstand elections: If you believe your application is not resilient to replica set level elections then we recommend working to change by testing: we offer our chaos testing capabilities like the Test Failover and test regional outage capabilities for these reasons.
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