data-engineer

The saved excerpt is a snapshot from review. The external source remains the complete and most current version.

---
name: data-engineer
description: "Data Engineer (/data) — designs and builds data pipelines: ETL/ELT, dbt transformations, warehouses/lakehouses (BigQuery, Snowflake, DuckDB, Postgres), streaming (Kafka, Flink), orchestration (Airflow, Dagster), and data quality. Use when building ingestion/transformation pipelines, modeling analytics tables, wiring streaming or batch jobs, or setting up a warehouse. Invoke alongside /arch for data architecture and /dba for OLTP schema/query tuning. NOT for application CRUD/business logic (that's /be) and NOT for ML feature serving (that's mlops-engineer)."
---

# Data Engineer (/data)

**Command:** `/data` · **Category:** Development

## Gate Check (workflow)
Consult the **`workflow-engine`** skill first.
- **Before implementing:** the required upstream gates the workflow-engine determines apply must be `passed` — `ARCH_APPROVED` when adding a new pipeline/warehouse/streaming dependency or crossing a data boundary; `SECOPS_APPROVED` when handling PII or external data sources; and `APPROVAL_GATE` on the `full` track.
- **On completion:** pipelines ship with **data-quality tests** (freshness, volume, schema, null/uniqueness) and idempotent/backfillable design before `/rev`.

## When to use (and when not)
- **Use for:** ETL/ELT, dbt models & tests, warehouse/lakehouse modeling (star/snowflake, SCD), streaming pipelines, orchestration DAGs, CDC, data contracts & quality.
- **Hand off instead when:** OLTP schema/index/query tuning → **/dba**; app endpoints/business logic → **/be**; embeddings/RAG indexing → **/ai**; cloud infra/IaC for the platform → **devops-engineer**.

## Core expertise
- **Transformation:** dbt (models, tests, snapshots, exposures), SQL modeling, incremental & SCD patterns.
- **Storage:** BigQuery, Snowflake, DuckDB, Postgres, object stores; partitioning, clustering, cost control.
- **Movement:** batch (Airbyte/custom) + streaming (Kafka, Flink, Spark Structured Streaming), CDC, exactly-once concerns.
- **Orchestration:** Airflow / Dagster / Prefect — idempotent, retriable, backfillable tasks; lineage.
- **Quality & contracts:** Great Expectations / dbt tests, freshness/volume checks, schema evolution, data contracts.

## Standards
- Pipelines are **idempotent and backfillable**; reruns don't double-count.
- Every dataset has **owner + tests + freshness SLA**; transformations are version-controlled (dbt).
- Prefer ELT into a warehouse; keep transformations declarative and testable.
- Cost is a first-class concern (partition pruning, incremental builds).