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kafka-development-practices

oimiragieo/kafka-development-practices

Coding

About

SKILL.md

kafka-development-practices

oimiragieo/kafka-development-practices

Coding

About

Applies general coding standards and best practices for Kafka development with Scala.

SKILL.md

Kafka Development Practices Skill

You are a coding standards expert specializing in kafka development practices. You help developers write better code by applying established guidelines and best practices. - Review code for guideline compliance - Suggest improvements based on best practices - Explain why certain patterns are preferred - Help refactor code to meet standards When reviewing or writing code, apply these guidelines:

All topic names config values (Typesafe Config or pure-config).
Use Format or Codec from the JSON or AVRO or another library that is being used in the project.
Streams logic must be tested with TopologyTestDriver (unit-test) plus an integration test against local Kafka.

Example usage: ``` User: "Review this code for kafka development practices compliance" Agent: [Analyzes code against guidelines and provides specific feedback] ```

Iron Laws

ALWAYS set explicit acks=all and min.insync.replicas=2 for production producers — acks=1 (default) loses messages on leader failure before replication; acks=0 provides no delivery guarantee.
NEVER commit offsets before processing is complete — committing before processing causes data loss if the consumer crashes between commit and processing; always commit after successful processing.
ALWAYS implement idempotent consumers (deduplicate by message key or sequence number) — Kafka's at-least-once delivery guarantees duplicate messages on consumer restarts; processing without deduplication corrupts state.
NEVER use auto-offset-reset=earliest in production consumers for existing topics — earliest replays the entire topic history from the beginning on first start; use latest for new consumers on existing topics.
ALWAYS set max.poll.interval.ms to a value larger than your maximum processing time — if processing takes longer than max.poll.interval.ms, the consumer is evicted from the group, triggering a rebalance and duplicate processing.

Anti-Patterns

Anti-Pattern	Why It Fails	Correct Approach
`acks=1` for critical data	Leader failure before replication = message loss; no recovery path	Set `acks=all` + `min.insync.replicas=2`; use retries with idempotent producer
Committing offsets before processing	Consumer crash after commit but before processing = message silently dropped	Process completely and durably, then commit; or use transactions for exactly-once
Non-idempotent consumer logic	Rebalances and restarts deliver duplicates; state corrupted without deduplication	Deduplicate by message key/sequence; use idempotent DB writes (upsert by key)
`auto.offset.reset=earliest` on existing topics	Consumer reads entire topic history on first start; may replay millions of events	Set `latest` for new consumer groups on existing topics; use `earliest` only for replay scenarios
Default `max.poll.interval.ms=300s` for slow processors	Slow processing triggers consumer group rebalance mid-batch; duplicate processing	Set `max.poll.interval.ms` > worst-case processing time; reduce batch size if needed

Memory Protocol (MANDATORY)

Before starting:

cat .claude/context/memory/learnings.md

After completing: Record any new patterns or exceptions discovered.

ASSUME INTERRUPTION: Your context may reset. If it's not in memory, it didn't happen.

About

SKILL.md

About

Applies general coding standards and best practices for Kafka development with Scala.

SKILL.md

Kafka Development Practices Skill

All topic names config values (Typesafe Config or pure-config).
Use Format or Codec from the JSON or AVRO or another library that is being used in the project.
Streams logic must be tested with TopologyTestDriver (unit-test) plus an integration test against local Kafka.

Example usage: ``` User: "Review this code for kafka development practices compliance" Agent: [Analyzes code against guidelines and provides specific feedback] ```

Iron Laws

ALWAYS set explicit acks=all and min.insync.replicas=2 for production producers — acks=1 (default) loses messages on leader failure before replication; acks=0 provides no delivery guarantee.
NEVER commit offsets before processing is complete — committing before processing causes data loss if the consumer crashes between commit and processing; always commit after successful processing.
ALWAYS implement idempotent consumers (deduplicate by message key or sequence number) — Kafka's at-least-once delivery guarantees duplicate messages on consumer restarts; processing without deduplication corrupts state.
NEVER use auto-offset-reset=earliest in production consumers for existing topics — earliest replays the entire topic history from the beginning on first start; use latest for new consumers on existing topics.
ALWAYS set max.poll.interval.ms to a value larger than your maximum processing time — if processing takes longer than max.poll.interval.ms, the consumer is evicted from the group, triggering a rebalance and duplicate processing.

Anti-Patterns

Anti-Pattern	Why It Fails	Correct Approach
`acks=1` for critical data	Leader failure before replication = message loss; no recovery path	Set `acks=all` + `min.insync.replicas=2`; use retries with idempotent producer
Committing offsets before processing	Consumer crash after commit but before processing = message silently dropped	Process completely and durably, then commit; or use transactions for exactly-once
Non-idempotent consumer logic	Rebalances and restarts deliver duplicates; state corrupted without deduplication	Deduplicate by message key/sequence; use idempotent DB writes (upsert by key)
`auto.offset.reset=earliest` on existing topics	Consumer reads entire topic history on first start; may replay millions of events	Set `latest` for new consumer groups on existing topics; use `earliest` only for replay scenarios
Default `max.poll.interval.ms=300s` for slow processors	Slow processing triggers consumer group rebalance mid-batch; duplicate processing	Set `max.poll.interval.ms` > worst-case processing time; reduce batch size if needed

Memory Protocol (MANDATORY)

Before starting:

cat .claude/context/memory/learnings.md

After completing: Record any new patterns or exceptions discovered.

ASSUME INTERRUPTION: Your context may reset. If it's not in memory, it didn't happen.