Downtime in Opensearch managed Configuration Changes

Question

I was reading about how configuration changes in opensearch managed are handled. So basically once we scale up by:
1) Increasing EBS storage
2) Increasing nodes
3) Switch to larger instance type
All these 3 create blue/green deployment where blue is the current cluster and aws creates another environment with the new configurations and copies all data from blue to green and once green is ready, aws switches all traffic from blue to green. The old blue nodes are all deleted. If failed then it will revert to the blue state.

Now I have 2 questions: 
1) Will creating a new environment and migrating all the data have some downtime or will aws switch to green only after all migration is done which means ZERO downtime?
2) Now based on load if I want to frequently scale up and down then this migration will be expensive right for creating a new environment each time and have 2 different types of configurations running simultaneously till the green is ready. What is the impact on cost due to this repeated scaling up and down.

TheQuietBuilder · Answer

Downtime & Cost During OpenSearch Configuration Changes

Thanks for raising this — it’s an important operational question.

🔹 Downtime:
AWS OpenSearch uses blue/green deployments to avoid downtime. It spins up a new (“green”) environment with the desired config changes, syncs data from the current cluster (“blue”), and only cuts traffic over when the green environment is healthy. So under normal conditions: zero downtime.

🔹 Cost Impact:
Yes, there is temporary double resource usage during this process. You’ll be billed for both environments while green is being provisioned and data is being replicated. If you're scaling frequently, this can become costly — especially when changing instance types or node counts.

Suggestions to reduce impact:

Combine multiple changes into one operation

Schedule scale-ups during low-traffic periods

Use Index State Management or Auto-Tune for intelligent scaling

Would be happy to expand on any of these options if helpful.

Downtime in Opensearch managed Configuration Changes

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