# Flink

> Apache Flink stream processing expertise for stateful computations over bounded and unbounded streams. Use when the user mentions Flink, Flink SQL, Table API, DataStream API, CDC, Kafka-to-Flink pipelines, checkpoints, savepoints, watermarks, windows, Flink Kubernetes Operator, or Flink integrations with Iceberg, Paimon, or Fluss.

- Skill: `kilo-org/flink` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add kilo-org/flink`
- Raw SKILL.md: https://api.skillmd.com/api/skills/kilo-org/flink/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- Author: Kilo-Org (https://skillmd.com/u/kilo-org)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/kilo-org/flink

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# Apache Flink Data Streaming Expert

Use this skill for production Flink architecture, operations, SQL/DataStream implementation, upgrade planning, and lakehouse streaming integrations.

## Current Facts

- **Current Flink line:** 2.2.x. Downloads include Apache Flink 2.2.1, while the site still labels 2.2.0 as the latest stable line.
- **Maintained 2.x patch lines:** 2.2.1, 2.1.2, 2.0.2.
- **1.x maintenance line:** 1.20.4. Use this as the 1.x migration baseline unless the project is pinned elsewhere.
- **Kubernetes Operator:** 1.15.0, compatible with Flink 2.2.x, 2.1.x, 2.0.x, 1.20.x, and 1.19.x.
- **Flink CDC:** 3.6.0, with artifacts for Flink 1.20.x and 2.2.x.
- **Java:** Flink 2.x requires Java 11+; Java 17 is the practical default for new deployments.

## Critical 2.x Notes

- DataSet API removed; use DataStream, Table API, or SQL.
- Scala DataStream/DataSet APIs removed from the core distribution.
- SourceFunction/SinkFunction and Sink V1 patterns are obsolete; prefer Source/Sink V2 connectors.
- `flink-conf.yaml` was replaced by standard YAML `config.yaml` in Flink 2.x.
- Per-job deployment mode was removed; use Application mode or Kubernetes Operator patterns.
- Validate savepoint compatibility carefully before 1.x to 2.x migrations.

## How To Use

1. Classify the request: SQL/Table API, DataStream, deployment, operations, upgrade, CDC, or lakehouse sink/source.
2. For new greenfield work, prefer Flink 2.2.x plus current connector artifacts.
3. For migration work, identify the exact source version, connector versions, state backend, and savepoint strategy before recommending commands.

## Production Defaults

- Enable checkpointing for streaming jobs and set explicit checkpoint storage.
- Use savepoints for planned upgrades and topology changes.
- Use watermarks and allowed lateness deliberately; make event-time assumptions visible.
- Monitor checkpoint duration, alignment time, backpressure, restart count, and state size.
- Prefer the Kubernetes Operator for long-running production jobs on Kubernetes.
- Use Iceberg/Paimon/Fluss connectors only at versions compatible with the selected Flink line.

## Update Checklist

- Recheck Flink downloads for core, CDC, connector, and Kubernetes Operator versions.
- Update Helm/doc URLs when operator versions change.