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)