Catalog

Walkthrough
Lines 1–8 pull `items` from the cache with no validation. Lines 10–18 loop and sum `item.price * item.qty`. Lines 20–22 return the total as a float.

Assumptions
1. The cache always returns a list → None raises AttributeError at line 10.
2. Every item has `price` and `qty` → legacy rows without `qty` raise KeyError mid-loop; partial sums are lost.
3. `price` is numeric → a string price silently concatenates on some paths. Dangerous.
4. The list is not mutated during iteration → a concurrent cache refresh mutates it; totals come back inconsistent with no error. Dangerous.
5. An empty list means a zero total → returns 0 silently; callers cannot tell "no items" from "free". Dangerous.

Verdict on your concerns: concurrency — unsafe; error handling — none; empty list — silent zero.

Tests
- items = None → a clear 500 with a logged cause
- one item missing qty → validation error naming the item id
- 10k items during a cache refresh → a consistent snapshot or a retry

Confirm the diagnosis and I will propose a patch.

Node list
1. Stripe Trigger — fires on checkout.session.completed — reads nothing upstream.
2. Notion — Create database page in "Customers" — Email ← $json.customer_details.email; Plan ← $json.metadata.plan; Amount ← $json.amount_total / 100; Date ← $json.created.
3. Slack — Post to #revenue — "New paid signup: {email} on {plan} ({amount} USD)" built from the same fields.

Workflow JSON: attached below, importable; credentials referenced as "Stripe account", "Notion workspace", "Slack bot" — create those three in Credentials before activating.

Error path: Error Trigger workflow "Alerts" → Slack #ops with the failing workflow name, the item's customer email, and the error message.

Test plan: in the Stripe Trigger node, click "Listen for test event", then send a test checkout.session.completed from the Stripe dashboard → Notion shows one row with the four fields → Slack shows one message → execution list shows green.

Smallest v1: this is already the smallest version (3 nodes). Add the welcome email as node 4 next week, after you have watched this run for a few days.