data-pipeline-engineer

license	Apache-2.0
name	data-pipeline-engineer
description	Expert data engineer for ETL/ELT pipelines, streaming, data warehousing. Activate on: data pipeline, ETL, ELT, data warehouse, Spark, Kafka, Airflow, dbt, data modeling, star schema, streaming data, batch processing, data quality. NOT for: API design (use api-architect), ML training (use ML skills), dashboards (use design skills).
allowed-tools	Read,Write,Edit,Bash(dbt:*,spark-submit:*,airflow:*,python:*)
category	Data & Analytics
tags	["etl","spark","kafka","airflow","data-warehouse"]
pairs-with	[{"skill":"api-architect","reason":"APIs that consume pipeline data"},{"skill":"devops-automator","reason":"Orchestrate pipeline infrastructure"}]

Data Pipeline Engineer

Expert data engineer specializing in ETL/ELT pipelines, streaming architectures, data warehousing, and modern data stack implementation.

Quick Start

1. Identify sources - data formats, volumes, freshness requirements
2. Choose architecture - Medallion (Bronze/Silver/Gold), Lambda, or Kappa
3. Design layers - staging → intermediate → marts (dbt pattern)
4. Add quality gates - Great Expectations or dbt tests at each layer
5. Orchestrate - Airflow DAGs with sensors and retries
6. Monitor - lineage, freshness, anomaly detection

Core Capabilities

Capability	Technologies	Key Patterns
Batch Processing	Spark, dbt, Databricks	Incremental, partitioning, Delta/Iceberg
Stream Processing	Kafka, Flink, Spark Streaming	Watermarks, exactly-once, windowing
Orchestration	Airflow, Dagster, Prefect	DAG design, sensors, task groups
Data Modeling	dbt, SQL	Kimball, Data Vault, SCD
Data Quality	Great Expectations, dbt tests	Validation suites, freshness

Architecture Patterns

Medallion Architecture (Recommended)

BRONZE (Raw)     → Exact source copy, schema-on-read, partitioned by ingestion
      ↓ Cleaning, Deduplication
SILVER (Cleansed) → Validated, standardized, business logic applied
      ↓ Aggregation, Enrichment
GOLD (Business)   → Dimensional models, aggregates, ready for BI/ML

Lambda vs Kappa

• Lambda: Batch + Stream layers → merged serving layer (complex but complete)
• Kappa: Stream-only with replay → simpler but requires robust streaming

Reference Examples

Full implementation examples in ./references/:

File	Description
dbt-project-structure.md	Complete dbt layout with staging, intermediate, marts
airflow-dag.py	Production DAG with sensors, task groups, quality checks
spark-streaming.py	Kafka-to-Delta processor with windowing
great-expectations-suite.json	Comprehensive data quality expectation suite

Anti-Patterns (10 Critical Mistakes)

1. Full Table Refreshes

Symptom: Truncate and rebuild entire tables every run Fix: Use incremental models with is_incremental(), partition by date

2. Tight Coupling to Source Schemas

Symptom: Pipeline breaks when upstream adds/removes columns Fix: Explicit source contracts, select only needed columns in staging

3. Monolithic DAGs

Symptom: One 200-task DAG running 8 hours Fix: Domain-specific DAGs, ExternalTaskSensor for dependencies

4. No Data Quality Gates

Symptom: Bad data reaches production before detection Fix: Great Expectations or dbt tests at each layer, block on failures

5. Processing Before Archiving

Symptom: Raw data transformed without preserving original Fix: Always land raw in Bronze first, make transformations reproducible

6. Hardcoded Dates in Queries

Symptom: Manual updates needed for date filters Fix: Use Airflow templating (e.g., ds variable) or dynamic date functions

7. Missing Watermarks in Streaming

Symptom: Unbounded state growth, OOM in long-running jobs Fix: Add withWatermark() to handle late-arriving data

8. No Retry/Backoff Strategy

Symptom: Transient failures cause DAG failures Fix: retries=3, retry_exponential_backoff=True, max_retry_delay

9. Undocumented Data Lineage

Symptom: No one knows where data comes from or who uses it Fix: dbt docs, data catalog integration, column-level lineage

10. Testing Only in Production

Symptom: Bugs discovered by stakeholders, not engineers Fix: dbt --target dev, sample datasets, CI/CD for models

Quality Checklist

Pipeline Design:

• Incremental processing where possible
• Idempotent transformations (re-runnable safely)
• Partitioning strategy defined and documented
• Backfill procedures documented

Data Quality:

• Tests at Bronze layer (schema, nulls, ranges)
• Tests at Silver layer (business rules, referential integrity)
• Tests at Gold layer (aggregation checks, trend monitoring)
• Anomaly detection for volumes and distributions

Orchestration:

• Retry and alerting configured
• SLAs defined and monitored
• Cross-DAG dependencies use sensors
• max_active_runs prevents parallel conflicts

Operations:

• Data lineage documented
• Runbooks for common failures
• Monitoring dashboards for pipeline health
• On-call procedures defined

Validation Script

Run ./scripts/validate-pipeline.sh to check:

• dbt project structure and conventions
• Airflow DAG best practices
• Spark job configurations
• Data quality setup

External Resources

• dbt Best Practices
• Airflow Best Practices
• Great Expectations Docs
• Delta Lake Guide
• Kafka Streams