java-kafka-reliability

name	java-kafka-reliability
description	Use this skill when statically reviewing a Kafka producer/consumer pipeline for whether it actually delivers the delivery semantics it claims — idempotent-producer-vs-exactly-once conflation, transactional read-process-write wiring (transactional.id, initTransactions, sendOffsetsToTransaction, consumer isolation.level=read_committed), at-least-once with or without an idempotent consumer, commit-before-process message loss, ordering (max.in.flight.requests.per.connection combined with idempotence), consumer lag as the operational SLA signal, max.poll.interval.ms rebalance stalls, DLQ/retry-topic design, and acks=all plus min.insync.replicas durability. Trigger when a user provides producer/consumer configuration, Kafka client or Spring @KafkaListener code, or a topic/partition design and asks whether messages can be lost, duplicated, reordered, or stuck, or whether an "exactly-once" claim actually holds. Reads source and sanitized configuration only; it never opens a broker connection, produces or consumes a live message, or creates, alters, or deletes a topic.
allowed-tools	Read Grep Glob
metadata	{"author":"github: Raishin","version":"0.1.0","updated":"2026-07-17","category":"messaging","lifecycle":"experimental"}

Java Kafka Reliability Review

Purpose

This skill statically reviews a Kafka producer/consumer pipeline against the delivery-semantics model it claims to implement, rather than taking the claim at face value. It classifies the design as transactional exactly-once, at-least-once with an idempotent consumer, or at-least-once with no dedup strategy (a defect), and checks that classification against the concrete wiring: producer idempotence and transaction configuration, commit ordering relative to processing, in-flight-request ordering guarantees, consumer-lag observability, max.poll.interval.ms rebalance-stall exposure, dead-letter/retry-topic design, and acks/min.insync.replicas durability. It absorbs consumer-side idempotency (dedup key / upsert design) as its own concern.