Note that some features require support from the source cluster.

Feature	Source Cluster Requirement	Destination Cluster Requirement	Notes
Core mirroring and failover	2.1	4.x	Kafka 4 is compatible with old clients versions up to 2.1 included.
Failback (reverse mirroring)	4.x	4.x	Requires LME tracking on both sides, otherwise it will fallback and truncate to zero, effectively mirroring from scratch.
Share Groups	4.x	4.y	If the source doesn't support share groups, mirroring continues but share group offsets won't be synchronized.

Migration From MirrorMaker 2

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System tests will validate behavior under realistic production conditions:

Performance Benchmark: Measure replication throughput and latency across WAN.
Scalability Test: Replicate 1000 topics with 100,000 partitions across Log Convergence: Check log convergence after a series of leader elections in source and destination clusters.
Failover Test: Simulate source cluster failure, measure consumer recovery time.
Long-Running Stability: Run continuous replication for 7 days, verify no memory leaks or performance degradation.
Security Validation: Test all authentication mechanisms (SASL PLAIN, SCRAM, Kerberos, mTLS) via kafka-mirrors.sh config files.
Migration Test: Test migration from older Kafka versions.
Scalability Test: Replicate 1000 topics with 100,000 partitions across clusters.
Long-Running Stability: Run continuous replication for 7 days, verify no memory leaks or performance degradation.
Performance Benchmark: Measure replication throughput and latency across WAN.

Rejected Alternatives

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