W4 Starter — fetch.py + load.py Skeleton

# W4 Starter — Copy This Skeleton Outcome: fill the three TODO functions and pass all four self-checks below against the LOCAL fixture generator — no network, no hosted server. ```python # src/ingest/fetch.py import time from src.ingest.fixture import get_page # LOCAL fixture, not a server def fetch_page(resource: str, page: int, per_page: int = 100) -> dict: # TODO: call get_page(resource, page, per_page) # TODO: retry 3x with exponential backoff on 429/5xx # (simulate: raise on first call for page 2, succeed on retry) raise NotImplementedError def fetch_incremental(resource: str, since: str): # TODO: loop pages until an empty `data` list; skip rows with # updated_at int: # TODO: read data/parquet/{resource}/*.parquet # TODO: upsert into stg_{resource} on primary key inside ONE transaction # TODO: advance ingest_watermark to max(updated_at) only on success raise NotImplementedError ``` ## Self-checks before submitting (run in repo root) 1. `python -m src.ingest.fixture --check` — prints FIXTURE OK (200 orders / 2 pages, unique ids, monotonic `updated_at`). 2. Run fetch + load twice with no new data — staging counts identical the second time (idempotent re-run, ms 276 `done_when`). 3. Mutate one fixture row (change status, bump `updated_at` past the watermark) and re-run — exactly one row changes. 4. `findings/01_ingestion.md` records counts + watermark + re-run proof; kill a load mid-transaction and show the re-run reconciles in `findings/02_failure_drill.md` (ms 277). ```