cxc-dev-data

# Dev-Data — Data Engineering & Analysis Guide Activates by change surface for data pipelines, analytics, SQL-heavy work, schema evolution, backfills, and reporting. Production-grade data engineering patterns for building reliable data systems. Before data work, read [dev](../dev/SKILL.md) for classification, fast paths, rule authority, family invariants, verification, and safety; current/public evidence follows its [Conditional Routes](../dev/SKILL.md#conditional-routes). Use browser fetch/open/text/get-dom/snapshot only after candidate URLs exist and the claim needs browser-verifiable source evidence. ## When to Activate - Building data pipelines or ETL/ELT processes - Processing CSV, JSON, Parquet, or Excel files - Writing analytical SQL, warehouse/lakehouse queries, or transformation models - Setting up data quality checks or validation - Performing data analysis, aggregation, or reporting - Choosing between batch and streaming architectures **Do not activate for plain app CRUD SQL, OLTP query tuning, or transactional schema design.** Route those to `dev-backend/references/stacks/database.md`. This skill owns analytics, ETL/ELT, pipelines, data quality, and reporting. ## Modular References | Condition | Reference | |---|---| | Every data task; ingestion, incremental loading, ETL/ELT, dbt, retries, or orchestration | [Principles and pipelines](references/01-ingestion-pipelines.md) | | Quality checks, data contracts, schema changes/backfills, review, or delivery | [Quality and evolution](references/02-quality-evolution.md) (DATA-MIGRATION-01, DATA-REVIEW-01) | | Analysis/reporting, batch/streaming, storage, or engine selection | [Analysis and engines](references/03-analysis-engines.md), [streaming](references/streaming.md), [tools](references/tools.md) | | ML training, experiments, feature stores, or data versioning | [ML pipelines](references/ml-pipeline.md) | | PII, retention, masking, or governance | [Governance](references/04-governance-queries.md#7-data-governance--pii), [implementation patterns](references/governance.md); `cxc-dev-security` for policy | | Analytical SQL/query execution safety, pipeline APIs, observability, or consumers | [Queries and companions](references/04-governance-queries.md#8-query-performance-guidelines) |