Kafka: Experience designing, building, and operating Kafka-based event streaming platforms—topics/partitions, producers/consumers, consumer groups, schema/serialization (Avro), Kafka Connect/Streams, security (ACLs/TLS), monitoring and tuning. Backend (Java/Spring Boot) expert: Java: strong OOP + functional style, concurrency, collections, memory/perf awareness; can read thread dumps/heap dumps and profile hotspots.