Version

3.5.1

Describe the problem you're encountering

After upgrading from CouchDB 3.4.2 -> 3.5.1, we are seeing stability regressions in both:

• Single node environments (OOM kill crash)
• 3 node clustered environments (full cluster outage during rolling upgrade)
  These environments were stable on 3.4.2 under same workloads
  The main symptoms include:
• Increased Erlang VM RSS memory usage (beam.smp)
• Very large Erlang process counts post-upgrade
• CPU spikes during compaction/rebalancing
• Cluster becoming unavailable during node cycling

Expected Behaviour

• CouchDB 3.5.1 should not significantly increase baseline memory/process usage on the same workload
• Single node instances should not be OOM killed under normal compaction load
• Rolling node upgrades should not result in full cluster outage

Steps to Reproduce

We have observed the issues under the following conditions:

• Upgrade CouchDB 3.4.2 → 3.5.1 (Erlang/OTP 26)
• Run with medium memory nodes (~8GB RAM)
• Large shard count / very high DB count
• Compaction or shard movement occurring
• Cycle one node during rolling upgrade (ASG refresh)

Result: memory/process growth and potential node loss -> cluster unavailability

Your Environment

Deployment

• AWS EC2 instances with persistent couch_data
• CouchDB nodes managed via ASG refresh (one node at a time)
• HAProxy + Fauxton access through fronted endpoint

Cluster configuration:

• 3-node cluster (n=3, q=1)
• Placement: primary / secondary / trinary
• Data size: ~319k databases
• Disk usage: ~640GB used of ~1TB per node

Instance resources:
~7.6GB RAM

Additional Context

No response