chini-002-checkout

E-commerce Checkout with Idempotent Payments

Process checkouts without ever charging a customer twice. Survive a downstream payment-API outage.

Source: Classic system-design interview corpus (Stripe / payment gateway design)

Prompt

Design a checkout system that takes a cart and processes payment.

Functional:
- POST /checkout accepts an order, returns an order id.
- Payment is processed via an external payment provider that may time out.
- Every checkout must be idempotent: a retried checkout must NOT charge the user twice.

Non-functional:
- Survive a 5x peak (e.g., flash sale) without dropping more than 5% of orders.
- Survive a slow payment provider (added latency) without blocking the whole queue.
- Survive a brief payment-provider outage by queueing or circuit-breaking.

Return a Chinilla CanvasState. Include a queue, a retry behavior, and a circuit-breaker on the payment-provider edge.

Constraints

Max components: 12
Required behaviors: queue, retry, circuitbreaker
Monthly budget: $800

Stress scenarios

Baseline orders

baseline

Steady checkout traffic.

5x flash sale

spike

Order volume spikes 5x for the duration.

Slow payment provider

latency

Payment provider response time grows by 1500ms.

Payment provider outage

outage

Payment provider is down. System must queue or fail safely (no double-charge).

Pass criteria (overall)

Min stability score: 75
Max drop rate: 3.0%
Min delivery rate: 95.0%
Max errors: 3

Submit your run

Submissions go through the chini-bench CLI. It calls your model with your key, scores the result locally, and posts to the leaderboard. Nothing leaves your machine except the canvas it produces.

End-to-end:

pip install git+https://github.com/collapseindex/chini-bench-cli.git
export OPENROUTER_API_KEY=...

chini-bench run chini-002-checkout \
  --provider openrouter --model google/gemini-2.0-flash-001 \
  --as alice --x alice --linkedin alice-builds

Or inspect the prompt first:

chini-bench prompt chini-002-checkout

Providers: openai · anthropic · google · openrouter · ollama

Leaderboard

Rank	Submitter	Model	Score	Stability	Delivery	Design	Pass	Links
#1	alex default	A anthropic/claude-sonnet-4.6	94	87.0	100.0	100.0	✓	X
#2	alex default	O openai/gpt-5.4	89	75.0	100.0	100.0	✓	X
#3	alex default	X x-ai/grok-4.20	86	69.0	100.0	100.0	✗	X
#4	alex default	G google/gemini-3.1-pro-preview	80	56.0	100.0	100.0	✗	X

Per-scenario breakdown of the top run

Scenario	Health	Drop rate	Delivered	Pass
baseline	87.0	0.0%	60	✓
flash-sale	85.0	0.0%	300	✓
payment-slow	87.0	0.0%	15	✓
payment-outage	88.0	0.0%	12	✓

How is this scored? →