Kafka Client Migrations With KCP and Confluent Cloud Gateway

Kafka Copy Paste (KCP), an open source CLI tool, now integrates with Confluent Cloud Gateway to automate the client migration phase of Kafka migrations. Previously, steps 1–3 (discovery, provisioning, data migration) were automated; now step 4 (client cutover) is also handled. Gateway acts as a transparent proxy that routes Kafka traffic, translates authentication mechanisms (e.g., SASL/SCRAM to API keys), and syncs consumer offsets via Cluster Linking. The migration workflow uses three KCP commands: `kcp migration init` for validation and planning, a lag-monitoring command to confirm replication readiness, and `kcp migration execute` for the atomic cutover. The cutover takes roughly 16 seconds, with consumers experiencing zero downtime due to offset syncing and producers buffering briefly. Group-based migration allows teams to migrate subsets of topics and clients independently, reducing blast radius. Rollback is supported until topic promotion completes. Future work includes traffic-plane-aware migration to move consumers and producers independently.