$npx -y skills add vaquarkhan/data-engineering-agent-skills --skill etl-elt-and-modernization-strategyGuides agents through ETL, ELT, and transformation-modernization decisions. Use when choosing execution boundaries, redesigning transformation layers, or moving from legacy ETL estates to warehouse- or lakehouse-centered ELT patterns.
| 1 | # ETL ELT And Modernization Strategy |
| 2 | |
| 3 | ## Overview |
| 4 | |
| 5 | Use this skill when the hard part is not a single job, but deciding where transformations should run and how a data estate should modernize over time. It helps agents reason about `ETL` versus `ELT`, pushdown versus external compute, orchestration boundaries, migration sequencing, and proof of parity during modernization. |
| 6 | |
| 7 | ## When to Use |
| 8 | |
| 9 | - choosing between `ETL`, `ELT`, or hybrid transformation patterns |
| 10 | - moving from legacy ETL tools into warehouse, dbt, Spark, or lakehouse execution |
| 11 | - redesigning ingestion and transformation boundaries across raw, curated, and publish layers |
| 12 | - reducing operational sprawl caused by duplicate transformation logic |
| 13 | - modernizing batch-first estates without breaking existing delivery expectations |
| 14 | |
| 15 | Do not assume `ELT` is always better just because the warehouse is powerful. |
| 16 | |
| 17 | ## Workflow |
| 18 | |
| 19 | 1. Define the transformation problem clearly. |
| 20 | Clarify: |
| 21 | - source latency and volume |
| 22 | - data quality expectations |
| 23 | - transformation complexity |
| 24 | - cost sensitivity |
| 25 | - publish or consumption latency |
| 26 | |
| 27 | 2. Map the current execution estate. |
| 28 | Include: |
| 29 | - where extraction happens |
| 30 | - where transformations happen today |
| 31 | - what logic is duplicated across tools |
| 32 | - where lineage or observability breaks |
| 33 | - what jobs are hardest to change safely |
| 34 | |
| 35 | 3. Choose the right execution boundary. |
| 36 | Consider: |
| 37 | - `ETL` when data must be reshaped or protected before landing |
| 38 | - `ELT` when warehouse or lakehouse pushdown improves maintainability and scaling |
| 39 | - hybrid patterns when extraction, privacy controls, or heavy preprocessing must happen before durable load |
| 40 | |
| 41 | 4. Plan the modernization path. |
| 42 | Decide: |
| 43 | - what stays temporarily on the old path |
| 44 | - what moves first |
| 45 | - how parity will be measured |
| 46 | - how cutover and rollback will work |
| 47 | |
| 48 | 5. Prove the new shape operationally. |
| 49 | Require: |
| 50 | - reconciliation evidence |
| 51 | - cost and performance review |
| 52 | - lineage continuity |
| 53 | - ownership and support readiness |
| 54 | |
| 55 | ## Common Rationalizations |
| 56 | |
| 57 | | Rationalization | Reality | |
| 58 | | --- | --- | |
| 59 | | "Everything should become ELT." | Some workloads still need pre-load shaping, masking, or protocol-specific extraction controls. | |
| 60 | | "The ETL tool is the problem." | The real issue may be unclear ownership, poor contracts, or duplicated logic across layers. | |
| 61 | | "We can rewrite all transformations at once." | Big-bang modernization usually breaks parity, runbooks, and downstream trust. | |
| 62 | |
| 63 | ## Red Flags |
| 64 | |
| 65 | - the same business logic exists in extraction jobs, Spark, and warehouse SQL |
| 66 | - ETL versus ELT is chosen by tool preference instead of workload needs |
| 67 | - modernization plans skip parity, cutover, or rollback |
| 68 | - sensitive fields are moved into ELT layers without revisiting controls |
| 69 | |
| 70 | ## Verification |
| 71 | |
| 72 | - [ ] The transformation boundary matches the real workload constraints |
| 73 | - [ ] ETL, ELT, and hybrid choices are explicit rather than assumed |
| 74 | - [ ] Modernization sequencing, parity proof, and rollback are defined |
| 75 | - [ ] Cost, lineage, controls, and support ownership were considered together |