Overview
What this challenge is about.
Build an event-ingest API (Express + Redis Streams) that receives usage events with idempotency keys. Aggregate hourly into Postgres rollups using a windowed worker that survives restarts without double-counting. Sync hourly aggregates to a billing-engine subscription via webhooks (mocked Stripe-like API). Produce monthly invoices with a per-customer reconciliation report comparing raw event count → rollup → invoice. Deliver TypeScript reference code, a 5-page operational runbook, a reconciliation report for a 30-day replay, and 3 chaos tests (ingest restart, billing API outage, clock skew).
The Brief
What you'll do, and what you'll demonstrate.
Build a metered-billing pipeline that ingests usage events, aggregates without double-counting, and invoices accurately at month-end with full reconciliation.
Earning criteria — what you'll demonstrate
- Design idempotent event ingestion under retries and out-of-order delivery
- Build a windowed aggregator that survives worker restart without double-counting
- Integrate with a webhook-driven subscription billing API safely
- Produce reconciliation reports a CFO will sign off on
Program Fit
Where this fits in your program.
Sharpens the same skills your degree expects you to demonstrate.
Skills
Skills you'll demonstrate.
Each one shows up on your verified credential.
Careers
Roles this prepares you for.
Real titles. Real skill bridges. Pick the one closest to your trajectory.
Career mappings coming soon.