data-pipeline-patterns

Data Pipeline Patterns

ETL vs ELT Decision

| Kriter | ETL | ELT | |--------|-----|-----| | Transform location | Pipeline'da | Data warehouse'da | | Data volume | Küçük-orta | Büyük | | Flexibility | Düşük | Yüksek | | Cost | Compute-heavy | Storage-heavy | | Use case | Legacy, compliance | Modern analytics |

Batch vs Streaming

| Kriter | Batch | Streaming | |--------|-------|-----------| | Latency | Dakika-saat | Saniye-milisaniye | | Complexity | Düşük | Yüksek | | Cost | Düşük | Yüksek | | Use case | Reporting, ETL | Real-time alerts, dashboards | | Tool | Airflow, dbt | Kafka Streams, Flink |

Idempotency Patterns

# Pattern 1: Upsert
INSERT INTO target (id, name, updated_at)
VALUES (%(id)s, %(name)s, %(ts)s)
ON CONFLICT (id) DO UPDATE SET
  name = EXCLUDED.name,
  updated_at = EXCLUDED.updated_at

# Pattern 2: Partition overwrite
DELETE FROM target WHERE partition_date = '2026-03-14';
INSERT INTO target SELECT * FROM staging WHERE partition_date = '2026-03-14';

# Pattern 3: Checkpoint
last_checkpoint = get_checkpoint('pipeline_x')
new_data = source.query(f"WHERE updated_at > '{last_checkpoint}'")
process(new_data)
save_checkpoint('pipeline_x', max(new_data.updated_at))

Data Quality Framework

import pandera as pa

schema = pa.DataFrameSchema({
    "user_id": pa.Column(int, pa.Check.gt(0), nullable=False),
    "email": pa.Column(str, pa.Check.str_matches(r'^.+@.+\..+$')),
    "age": pa.Column(int, pa.Check.in_range(0, 150), nullable=True),
    "created_at": pa.Column(pa.DateTime, pa.Check.less_than_or_equal_to(pd.Timestamp.now()))
})

validated_df = schema.validate(df)  # Fail on invalid data

Quality Dimensions

| Dimension | Kontrol | Tool | |-----------|---------|------| | Completeness | NULL ratio < threshold | Great Expectations | | Accuracy | Value range checks | pandera | | Freshness | Last update < SLA | Airflow sensor | | Uniqueness | Duplicate check | SQL DISTINCT | | Consistency | Cross-table referential integrity | dbt test |

Pipeline Orchestration

# Airflow DAG
from airflow import DAG
from airflow.operators.python import PythonOperator

with DAG('daily_etl', schedule='0 6 * * *', catchup=False) as dag:
    extract = PythonOperator(task_id='extract', python_callable=extract_fn)
    transform = PythonOperator(task_id='transform', python_callable=transform_fn)
    load = PythonOperator(task_id='load', python_callable=load_fn)
    validate = PythonOperator(task_id='validate', python_callable=validate_fn)

    extract >> transform >> load >> validate

Checklist

• [ ] Pipeline idempotent (rerun safe)
• [ ] Data quality checks her adımda
• [ ] Dead letter queue (failed records)
• [ ] Monitoring + alerting aktif
• [ ] Schema evolution handled
• [ ] Backfill mekanizması var
• [ ] Retry logic (exponential backoff)
• [ ] Data lineage tracked

Anti-Patterns

• Pipeline'da hardcoded credentials
• Idempotent olmayan transform
• Data quality check'siz load
• Monolithic pipeline (parçala)
• Silent failure (error swallowing)