Shopify Price & Stock Monitor — Apify Actor (deploy-ready, not yet published)

Reads any Shopify store's public /products.json catalogue feed and returns clean per-variant rows (price, compare-at price, availability, SKU, vendor, tags) plus a run summary. Pass a previous run's rows back in as a snapshot and every variant is flagged for price changes, stock-outs, restocks and new arrivals — built for competitor price tracking, catalogue audits and scheduled price/stock alert pipelines (Make/Zapier/n8n via Apify schedules + webhooks).

Status: built and locally verified 2026-10-29 (offline sample test, change-detection test, live test — all below). Deployed to Brian's account unpublished, no pricing set; publishing is a separate approved step.

Why this product (scan summary, Oct 2026)

This was the strong #2 in the Actor #1 niche scan: real merchant pain (competitor price/stock watching), and the data source is the store's own public feed — no login, no browser, no proxies, so pay-per-event economics can't go negative (same structural safety as Actor #1). Change detection is the differentiator vs raw catalogue scrapers: they sell rows, this sells "what changed since yesterday?" in one scheduled run.

Input (.actor/input_schema.json)

Output (per variant row)

store, productId, productTitle, handle, productUrl, vendor, productType, tags, variantId, variantTitle, price, compareAtPrice, available, sku, fetchedAt, priceChanged, oldPrice, wentOutOfStock, backInStock, isNew

Summary (SUMMARY key in the key-value store)

productCount, variantCount, outOfStockVariants, onSaleVariants, priceMin, priceMax, priceAvg, snapshotProvided

changes{priceChangedCount, wentOutOfStockCount, backInStockCount, newVariantCount, removedVariantCount}

Removed products are counted from the snapshot's variant IDs. Note (same caveat as comparable monitors): removal counts are only meaningful when the whole catalogue was read on both runs — a capped run can shift feed order.

Pricing (proposed, pay-per-event — in .actor/pay_per_event.json)

Sanity check against live Store pricing (Oct 29, 2026): the closest comparable, pistachio_implementation/shopify-catalog-monitor, charges $0.001 per product checked (+$0.005 per change); Media Pro Tools' Shopify scraper/monitor charges $0.0005 per product/variant row (+$0.002 per change); a generic product-page extractor charges $0.0015/row. The brief's first guess of $0.002/product sat above that whole band, so it was adjusted to $0.001/product — mid-band, at parity with the most comparable monitor, with margin protected by near-zero compute (plain HTTPS GETs).

Local tests (2026-10-29)

• Offline sample (tests/sample_products.json, 3 products / 5 variants): parsed exactly — string prices → floats, compare_at_price ""/null → null, 1 out-of-stock, 2 on sale, price avg 64.7.
• Change detection: mutated fixture (one price 120→99, one variant flipped to unavailable, one variant removed) against the first run as snapshot →

  priceChangedCount 1 (oldPrice 120.0), wentOutOfStockCount 1, removedVariantCount 1
  , all flags on the right rows.
• Live (allbirds.com, cap 30 products): 30 products → 328 variant rows, 222 out of stock, 20 on sale, prices 50.0–145.0 (avg 109.74).

Project layout

shopify-monitor/
├── .actor/
│   ├── actor.json            # name/title/description, dockerfile + schema pointers
│   ├── input_schema.json
│   ├── output_schema.json    # legacy output schema (templates, string types)
│   ├── dataset_schema.json   # dataset fields + table view
│   └── pay_per_event.json    # PPE pricing (proposed; NOT set on the platform)
├── Dockerfile                # apify/actor-python:3.12
├── requirements.txt          # core is stdlib-only; SDK from base image
├── src/
│   ├── core.py               # feed fetch/pagination, normalize, snapshot diff, summary
│   └── main.py               # thin Apify entrypoint (charges actor-start, product-scraped)
├── local_run.py              # offline/live test harness (no account needed)
└── tests/sample_products.json

Deployment

Deploy (unpublished, no pricing) via the connector helper:

python3 ~/workspace/custom-connectors/custom.apify/bin/apify.py deploy ~/workspace/apify/shopify-monitor

Publishing to the Store and applying the pricing above are separate, approval-gated steps.