Cluster size active active /active passive same??

cluster size will be same in active passive as active active

✅ No — cluster size in active-passive is typically smaller than in active-active.

But there’s nuance. Let’s break it down:

🔄 Cluster Size Comparison: Active-Active vs Active-Passive

Aspect	Active-Active	Active-Passive
Traffic handling	Both regions handle live traffic	Only one region handles live traffic
Cluster size (initial)	Full capacity in both regions	Full capacity in active, reduced in passive
Pod replicas	All services fully replicated	Services may be deployed with 0 replicas or in paused state in passive
Kafka	Fully running in both regions	Read-only replica or standby setup
DBs	Read/write in both regions	Primary write in active, read-only in passive
Autoscaling	Enabled in both	Only enabled in active region (passive off)
Cost	Higher (100%+100% capacity)	Lower (100% active, 30–60% passive until failover)

South India (Active): 100% capacity (e.g., 30–45 nodes)
West India (Passive): 40–50% hot standby capacity (e.g., 10–20 nodes)
- Kafka read replica or inactive
- Services deployed but paused or scaled to 0
On failover: passive cluster scales up automatically or via script

You save cost by not running full load in passive region unless it’s needed.

Component	State in Passive Region
AKS cluster	Deployed, lower node count (autoscaler enabled)
Microservices	Deployed, replicas = 0 or paused
Kafka brokers	Replicating topics, not processing events
Azure SQL / Cosmos	Read-only replica
Monitoring tools	Ready, but passive

If low RTO (Recovery Time Objective) is critical:

You may choose to pre-provision full capacity in passive cluster.
Otherwise, use auto-scaling triggers or runbooks to scale passive to active.

📉 Cost savings of ~30–50% with Active-Passive⏱️ Longer RTO unless passive scales preemptively